Is there a 'Blackface' type ~15w clone?

[The Captain]

Hi folks- Im after info for a build plan. Ive a 5e3 build and frankly hate it- too bassy (tried all to rid it) and Ive only heard its distortion once when the police came round from volume complaints (from the next street!)

SO, I wonder is there a chimy 'blackface' fixed bias type 12-15w design with a bass and treble (& ideally a MVol too) out there? I get a bit overwhelmed by the no. of fender models to pick exactly what could be a blueprint as it were. thanks for any help, Captain.

[hasserl]

The closest I think would be the Princeton Reverb.

[The Captain]

Yes I did see the Princeton but was bamboozled by the no of Fender's varieties ie some SE 5w, some 2x 6v6, and others with/ without reverb (not needed) and/ or proper tone controls (a must have). Id like to get more info if anyone's knows, a build in this ballpark with bass and treble pots + an MV would be the ticket. thanks

[MWJB]

If your 5E3 is too loud then I wouldn't go for another push pull Fender. Most Princetons put out over 15W in the range that folks typically play them. How about a BF Champ, with MV and a 25K mid control (not keen on the 15K stock mid resistor) with (wait for it...) fixed bias!

[The Captain]

Hi Mark- I thought Id pester some other ampers here! is the Princeton not simply a 5w champ with a tone pot? some Princetons seem to be 2x 6v6s, others SEs, so Im a bit confused there. Basically the wee PT from yourself (508v- 2 red HVs, 5v- 2 rectifier 2ndaries, and iirc 5v- 2 heater wires) Id like to use as a base for another fendery amp. The 5e3 was loud, yes, but Id like to have vol on tap so a 3w champ is a bit pokey I think. I wonder if the princeton reverb having the bass/ trb controls can be made without the reverb and with a MV? thoughts helpful.. Capt

[MWJB]

Tweed Princetons (5?2) amps were SE, cathode biased, 1x 6V6, basically as you say a Champ with a tone pot. 6G2 onwards were push pull, fixed bias, with a cathodyne PI. 6G2 had a tone pot only, later Princetons had Treb & Bass.

Later BF & SF (treb & bass) non-reverb Princetons don't have much gain, can sound a little sterile, low-ish gain PI and losses in the tone stack. If you built one without tremolo and used the spare 12AX7 triode as a tone stack recovery tube that would help get some gain back.

That PT has a little more heater capacity that the Princeton rating, but I susect the Princeton PT's are conservatively rated, I'd personally prefer a slightly better heater current rating and more B+ voltage for a push pull Princeton. Hence the Champ suggestion if you need treb & bass. A 5F2A Princeton, despite just having a tone control is also pretty flexible tonewise, definitely Fendery tones available.

[stokes]

Capt,try the Princeton 5E2.But use a 6l6GC for the power tube and a suitable OT.For your MV just replace the 220k grid resistor on pin 5 of the power tube with a 250k or 500k pot.I built something similar but used a tweed champ as the basis,no tone control,I used a hybrid type bias,it has a 75ohm resistor on the cathode and an adjustable fixed bias circuit as well,used a GZ34 rectifier and tried various NOS 6l6GC's and a 10 Weber speaker.Fender switched to the 2x6V6 in 1961 with the 6G2 circuit and never went back to the SE version of the Princeton,which was just a Champ with a different name.

[stokes]

Sorry,MWJB I was typing while you posted.

[The Captain]

Howdy Mr Stokes.. but I need one of these 5E2/ 5F2 types with 2 tone pots after all my trials with the 5e3. I did an MV mod similar on a Vjr, so that bit's easy enough it seems.

[stokes]

So are you saying you want to have more control in the tone stack with a treble and bass control as opposed to the single tone control of the 5E2/5F2?You could just build the Black Face preamp but sub the power section for a single ended output like the Tweed Princeton.So you would use the first stage from the BF into the tone stack/vol control then feed that into the driver stage and out put of the 5E2/5F2.

[The Captain]

Terrific.. that sounds a spot-on idea. Id like to know your opinion of my PT for this application Mr.Stokes http://www.torresamps.com/images/trans-25.gif its perhaps not ideal, but, using the site below as a build basis the clips do sound VERY promising and fendery using just a hammond 270FX (270v-0-270v presumably), ie hopefully not too dissimilar to mine.. & fwiw a 125?SE and a 5U4 is it? here: http://jameshadfield.com/Princetone.html

Grateful for any input of course, Captain.

[stokes]

That PT will be okay for a 6V6 output,but the 60ma rating on the HV supply will be marginal for a 6L6 type output tube,IMO.The Hammond 125ESE OT will be fine.As for the rectifier,the 5U4 has a 3amp heater draw,although the PT's 5v winding is 3amp,I like to have a little larger safety margin here,but if the 5U4 is all you have it will do,I'd prefer a 5V4.

[Satamax]

I was about to say, do as Stokes said, build a BF preamp, and a dual champish power section, two tubes, with one who can be switched out for less volume. It has been done before iirc.

Bye.

Max.

[MWJB]

Hi Stokes,

That 60mA rating on the B+ winding is an AC rating, not DC (had the same reservations & checked with mfr). Previously was in a 5E3 type build which even ran 6L6s (100mA draw) with no issues.

Cheers, Mark.

[The Captain]

Forgive my naiivity, but can someone point out why the BF Princeton's tone config can't be added to the 5e3? say turning the normal vol pot into the bass pot, and so the tone pot as the treble? (or suchlike) ie single channel with bass, treb and vol- as opposed to 2 channel's tone, vol and vol..?

[stokes]

Hi Stokes,

That 60mA rating on the B+ winding is an AC rating, not DC (had the same reservations & checked with mfr). Previously was in a 5E3 type build which even ran 6L6s (100mA draw) with no issues.

Cheers, Mark.

Very good,I was wondering about the 25watt rating with only 60ma's on that HV winding.

[stokes]

Forgive my naiivity, but can someone point out why the BF Princeton's tone config can't be added to the 5e3? say turning the normal vol pot into the bass pot, and so the tone pot as the treble? (or suchlike) ie single channel with bass, treb and vol- as opposed to 2 channel's tone, vol and vol..?

You have 250k pots in the BF Princeton,the 5E3 has 1M pots,it could be done,but the values of the components would have to be adjusted.There is a site that has a tone scaling section,I dont recall where I saw it,maybe somebody can point you to it.

[Bruce / Mission Amps]

Terrific.. that sounds a spot-on idea. Id like to know your opinion of my PT for this application Mr.Stokes http://www.torresamps.com/images/trans-25.gif its perhaps not ideal, but, using the site below as a build basis the clips do sound VERY promising and fendery using just a hammond 270FX (270v-0-270v presumably), ie hopefully not too dissimilar to mine.. & fwiw a 125?SE and a 5U4 is it? here: http://jameshadfield.com/Princetone.html

Grateful for any input of course, Captain.Is this the PT you used in the 5E3?
Did you also use a NOS 5Y3GT?
What output transformer did you use for the 5E3?

Why I ask now is that I am getting the feeling maybe you never built a real 5E3 clone anyhow so you really don't know what one sounds like.

[MWJB]

Hi Bruce,

The Captain used a Weber PT to start with (484v on the plates uncorrected - I've seen original tweed Deluxes run higher). It burned up. The replacement Weber ran very hot & high voltages. I offered a spare 2nd hand PT that admittedly ran lower B+ than a real 5E3 but as the Captain has noise issues with neighbours I figured a little earlier breakup wouldn't hurt.

Throughout the various PT's The Captain had issues with the tone.

But your point is a good one, when setting out to build your first amp a tonal reference is a must to ensure it really is doing what it's supposed to. Just ensuring voltages are ball park and connections are correct is not always enough. Better quality kits, with instructions, take out a lot of the guesswork. A bit more expensive? Yes, but when your tearing out your hair in frustration you'll be wishing you'd spent that bit extra.

[The Captain]

Bruce I do have this in the 5e3 at the mo, but have until recently had a 'proper' ish voltage Weber PT in (reson was the weber was hot, but it seems they just do that anyway). Fwiw now the chassis is just warm yes- soundwise though its only mildly flatter, otherwise its as annoyingly bassy as ever, hence I must have bass and treble pots on a 5** build or its really tonally useless to me. Im trying to figure out the BF Princeton applied to the 5e3 before I bin it, but its doing my head in figuring it out!

[The Captain]

Good point there. I can believe better PTs such as Missions will sound altogether better, but I think I just made the innitial mistake of plumping for the 5e3- soundclips from internet etc, never give any idea of the lower tones- and have spent lord knows how long thinking I had a prob when I didnt! Now Imho 5e3s were designed in the 50s for single coils only (obviously) but WITH an extra dose of low end to 'fill' the stage as it were, perhaps filling in, to an extent, for the bass register too. Therefore with my SG its all wrong, unless I can specifically alter its tone with 2 tone pots..

[MWJB]

Mount the tone caps and treble slope (100K) on the pots, then you can visually trace where they need to be, doubt you'll find room on the board anyway. Use the 2nd half of V1 as a tone recovery stage a la BF Princeton Reverb and every other BF amp apart from non-reverb Princeton.

[Satamax]

You have 250k pots in the BF Princeton,the 5E3 has 1M pots,it could be done,but the values of the components would have to be adjusted.There is a site that has a tone scaling section,I dont recall where I saw it,maybe somebody can point you to it.

Well, just made me think, on the tone stack calculator there's the james amps tonestack which has a one meg pot and a 470, may be it would be nice to do a baxandall tonestack in your tweed. :D

[The Captain]

This is a great plan to crack on with on the 5E3.

A closer look at the BF Princeton Rev shows 340v, 340v along to the rectifier pins 4 and 6: http://i102.photobucket.com/albums/m106/TheCaptain_02/princeton_reverb_aa1164_layout.gif

Now then, as my unused Weber PT has 680v secondaries (6.3v filaments, 5v other 2) could this be used to clone the whole shebang for a future project- or am I missing a trick.. I saw Weber DO use this exact PT for their clone of the circuit BUT using the PTs 'other pair' of 540v 2ndaries (the layout differs by using a 'WU4GB' recifier/ slightly differing 6v6gt wiring but otherwise exactly the same). Would anyone know why the 540v prefered, or any reason why I couldnt use the PT with the 680v pair as per the original above layout? (I did try these lower 540v 2ndaries as advised to run the PT cooler in the 5E3, but alas I got no sound at all).

Thanks for any ideas, Captain.

[Bruce / Mission Amps]

Bruce I do have this in the 5e3 at the mo, but have until recently had a 'proper' ish voltage Weber PT in (reson was the weber was hot, but it seems they just do that anyway). Fwiw now the chassis is just warm yes- soundwise though its only mildly flatter, otherwise its as annoyingly bassy as ever, hence I must have bass and treble pots on a 5** build or its really tonally useless to me. Im trying to figure out the BF Princeton applied to the 5e3 before I bin it, but its doing my head in figuring it out!Yes I recall the other threads now.
OK, a blackface Princeton is a very similar amp to a 5E3 but the Princeton uses the second triode of V1 to recover audio from the treble-bass-mid tone section and the other triode of V2 to make vibrato.

The major differences are the tone stack and the Princeton is fixed bias while the 5E3 Deluxe is cathode biased.
The phase inverter of the Princeton is almost the same as the tweed Deluxe so you can build a great sounding amp with two power tubes and two preamp tubes.

[The Captain]

Ive tried applying a Princeton Rev tone circuit to the 5E3 now, but alas I get just a loudish 'BRRR' from speaker. Can anyone spot a faux-pas here? thanks

http://i102.photobucket.com/albums/m106/TheCaptain_02/Picture326.jpg

go to..

http://i102.photobucket.com/albums/m106/TheCaptain_02/Picture327.jpg

In meantime Im thinking to just redo a BF fixed bias circuit entirely, & ideally with my PT- if anyone could remind me (lost track sorry) if its at all suitable for the Princeton Reverb circuit: (PT again http://www.torresamps.com/images/trans-25.gif). Cheers folks

[stokes]

Cant tell anything from the pictures,but I assume you are now only using one channel,in other words only one half of the first preamp tube is being used.In order to use both halves,or 2 channels, you would need 2 complete tone stacks,one for each half of the first tube.If you are trying to use one channel with the original 5E3 tone circuit and one with the Princeton Rev,it wont work.As for the PT,it will work for the BF circuit,but the voltages wont be exactly as the schem shows.

[The Captain]

Cant tell anything from the pictures

as per usual (I mirrored light up into pots for the shot too! hehe oh well). What I was trying was to single channel it adding a bass (L) and treb (middle pot) to the vol (R), to the V1/ V2 as the princeton reverb does. I shifted the dropping Rs from 4.7k and 22k to 1K and 4.7K too, amongst other wiring tinkerings- none done as guesswork- I was helped again patiently by MJWB to get the setup. Maybe its too long a shot to convert this way; perhaps its just telling me 'enough already with the 5E3'.. beaten me black and blue so it has.

So thanks Mr. Stokes- a fresh start is needed/ new circuit entirely. Can you point me twds a rectifier for above PT used for a BF Princeton Reverb ie, do I stay with the 5U4GB as the fender schem/ layout, try a weber WU4GB, or maybe I need a 'match'/ another for this PT (with a 125E fwiw).

Muchos muchos, Captain.

[MWJB]

Captain,

Where does the red wire from the centre tab of your volume pot go? Should go to V1 pin 7.

Wiring with a BF tonestack between V1a & V1b (using both halves of the first preamp tube) will work fine.

[MWJB]

OK spottedan error.

The yellow wire from coupling cap at V1, 1 should go to the free end of the 250pf cap on the treble pot. From this same junction the 100K resistor should then go to the junction of both the .1uf & .022uf caps on the bass pot.

You currently have the 100K in series with the yellow wire to the 250pf.

[MWJB]

Hard to see from the photo but neither the .1uf nor the .022uf on the bass pot should be grounded to the pot body (looks like they could be).

[The Captain]

OK spottedan error.

The yellow wire from coupling cap at V1, 1 should go to the free end of the 250pf cap on the treble pot. From this same junction the 100K resistor should then go to the junction of both the .1uf & .022uf caps on the bass pot.

You currently have the 100K in series with the yellow wire to the 250pf.

Hi Mark, thought you must be on hols so didn't pester..

Red wire does indeed go from vol mid lug to V1 pin 7 as to your previous post Q (neither bass caps grounded too).. and yellow wire does indeed go to free end of (680 pf) cap up at treb pot/ same junction the 100k (in pic tucked at fat bass caps feet) splits on to both bass caps.

I wonder if these are right though: this yellow wire mentioned, is starting on board at the junction of wire from V1 pin 1/ rhs 100k..
And from V2 pin 2 Ive a wire up to the top end of the (now only) .022 coupling cap, and a 470k to my gnd bolt on far right/ side of chassis..

[The Captain]

This should be clearer as to how Ive wired the pots/ yellow wire's starting place on board: if not, my diagram behind is exactly as its wired! (please ignore inferior caps as its a test.. if I can get this to work I'll replicate again with fancy caps)

http://i102.photobucket.com/albums/m106/TheCaptain_02/Picture348.jpg

[Dave H]

The 5E3 can be too bassy but don't give up on it. It can sound great with a few mods. Wire it up like this -

http://cdharris.members.beeb.net/15W 6V6 Guitar Amp.pdf

The bass problem will be gone and you won't miss the lack of bass/treble pots.

Dave H.

[The Captain]

Thanks David, it'd take me another week to go through that to see what's different and how to simplify/ apply it to a stock 5e3- Im having enough trouble just trying to figure the way Im attempting at the mo it seems! appreciate the link tho- Captain.

[MWJB]

Yes wire from V1 pin 1 goes to treble cap & 100K slope resistor (bridges treble cap to bass & mid caps).

Wire to V2, pin 2 should come from coupling cap at V1, pin 6. That 470K is the grid load for V2, pin 2 and is correct (save for any personal tweaking of its value).

[MWJB]

From your latest pic the tonestack looks correct in principle. If all connections are good, this is not where your problem lies.

[The Captain]

From your latest pic the tonestack looks correct in principle. If all connections are good, this is not where your problem lies.

Still no joy Mark- I rewired it back to 5e3 to check (it works) so rewired it back again with different tone caps (all continuity, connections, resoldered, using one channel only/ obviously checked which connected- thoughrally sure etc as always): as before- on flipping standby a 'BRR' & a loud huge bassy tone only (vol at 0, tones 4ish): turning any pot did nothing so quickly turned off..

The only different bits Im using are 2x 470k lin tone pots (250k log should be) and the 680pf (250pf)- Im sure tho I should get something ok soundwise even with these to show me its feasable. The only other thing I see is on the PReverb layout's is V2 having links across pins, 5e3 not, but Im sure Mark would be aware of these/ the slightly different configs between the circuits.

[MWJB]

Isolate at which stage the "BRRR" is being introduced.

Use a jumper lead to ground out the signal at V1, 2, then at V1, 7, then at V2, 2. Wherever the jumper lead is when the "BRR" stops, it's the stage between that and the last place where you had the jumper connected, where your problem is. With the vol at "0" that SHOULD mean that signal at V1, 7 is grounded out at that point - so double check V1, 6 to V2, 2 (this should be the only change that you have made to V2).

Draw a layout directly from your amp's wiring, NOT from any cannibalised layouts lying around (so that you are drawing what you have ACTUALLY done). Even better draw a schematic (best to get in the habit of reading schems rather than layouts), signal goes in on the grid (2 & 7) & out on the plate (1 & 6) - break each triode down on by one.

[The Captain]

Yes I redrew a simplified diagram using your info & the plan from both circuits to be stupidly clear so I couldn't possibly get it wrong: I see clearly where on PR circuit Im pinching, what Im altering, & what Im doing to replicate it. Just to reitterate what Ive done, as it bafflingly only sounds like a wiring mistake to me:

Tones and vol pots wired as pic.

V2 (pin 2 only now differs):
--added a wire to the top side (to be exact- on the board right beneath 1cm away from the bright no.2 input jack) to the now only one remaining .022 cap. The bttm side/ other end of this cap is the unchanged junction to V1 pin 6/ one of a pair of 100ks.
-- & added an extra 100k directly from V2 pin 2 wired on to my preamp 'star' gnd bolt..
So pin 2 is now a junction for 2 things, previously just one to normal vol pot.

V1 (pin 7 only now differs):
-- removed one channel's input wiring to pin 7, replacing this with a wire to vol pin 2.

Replaced dropping Rs:
4.7k 2W with a white squarish (fwiw) 1K 3W.
22k 2W with original 4.7k 2W (just swizzled it round 180*).

All continuity checked inc between adjacent pins, dropping rs, pots, input channel, n/c input channel etc etc. Not possible Im using n/c input pair (sound is heard anyway). Using 2x 12ax7s. Nothing else removed, cut or altered ie link between pins.

[MWJB]

With the exception that you should still have a second .022 coupling cap between V2, 1 & V2, 7 (it is there in your photo), that all sounds correct.

[The Captain]

Im damn nr 100% sure whats done is correct, Im just going thru -again- in child's language as it were to be stupidly clear (I can see schems no probs but its WAY quicker to use layouts especially if Im so very stuck- and immediately clear to draw what Ive done for help):

http://i102.photobucket.com/albums/m106/TheCaptain_02/Picture355.jpg

[MWJB]

That's spot on.

Have you identified at which stage you can turn off the "BRRR" by shorting the grid to ground yet? You have the overall concept, you just need to break it down to component parts to find & cure the problem.

[The Captain]

That's spot on.

Have you identified at which stage you can turn off the "BRRR" by shorting the grid to ground yet? You have the overall concept, you just need to break it down to component parts to find & cure the problem.

Hi Mark, I'll try this this ev now Im 100% sure it is correct; so rereading your previous post Im gonna..

1. use a std wire jumper, ie with no resistor in series, between V1 pin 2 and chassis for gnd- flipping both switches on and hoping it dont go pop.. then
2. repeating with pin 7 (Im turning off & waiting between these) taking link off pin 2.
3. repeating same with pin 7 of V2.

Just being stupidly careful to check, as I noted there was ~120V iirc read at V1, 1 on its birthday voltage checks (friday 13th feb probably).
Apologies for another laboured bore of a thread to whoever is daft enough to be still reading this spiel.. Captain.

[MWJB]

Yes, that's the plan. You can't be too careful.

[The Captain]

Tests done: 'BRR' stops when grounding out V2, pin 2 (both V1 pins 2 and 7 'BRR' with a 'pulsing' sound when grounding out I note here). I'll see if my brain can come up with any sense re. this this tonight.. probably not! cheers Mark,
Captain.

[MWJB]

So this tells you that the "Brrr" is being injected between V1, 6 and V2,2. If you pull V1 see if you still get "Brrr".

Pull V2, measure resistance to ground at V2, 2 - you should get 100K (your grid load resistor at V2,2). Then check continuity to top of coupling cap at V1, 6. If checks OK, suspect 0.22uf at V1, 6 (just replace it anyway, caps are cheap, make sure the cap legs are located in the relevant eyelets - not just resting on old component legs & soldered.)

If there's no change after that...I'll tune in again tomorrow...same time, same channel?

[The Captain]

So this tells you that the "Brrr" is being injected between V1, 6 and V2,2. If you pull V1 see if you still get "Brrr".

Pull V2, measure resistance to ground at V2, 2 - you should get 100K (your grid load resistor at V2,2). Then check continuity to top of coupling cap at V1, 6. If checks OK, suspect 0.22uf at V1, 6 (just replace it anyway, caps are cheap, make sure the cap legs are located in the relevant eyelets - not just resting on old component legs & soldered.)

If there's no change after that...I'll tune in again tomorrow...same time, same channel?


Ok I can understand prob lies between V1, 6 and V2, 2. Now I will try your suggestions above later tho im not sure exactly how Im testing; in meantime I just whipped out the .022 cap lying in this prob area replacing it with a .1 being only thing to hand: still bbrring.

So re the above tests- am I..

1. leaving V1 in or taking V1 out, or taking both out?
2. doing both the V2, 2 resistance check /and continuity from this coupling cap's top with amp on*, both switches flipped?
3. *but from where to where am I measuring this continuity? fwiw Ive measured continuity 10x across/ between each point on the preamp, 3x new bits added, indeed re-did the whole circuit again.. with amp off.. should this be on??

thoughrally confused of course.. Captain.

[MWJB]

For the resistance/continuity tests you don't need any valves in place, or the amp on.

Measure continuity from actual tube pin to component lead as it exits component body.

What 3 new bits have you added and why? Why have you "re-done the whole circuit", did you think the "whole circuit" is wrong? Because you are unsure, you are randomly throwing parts at the amp..STOP! You need to methodically find the specific cause of your problem and solve it. I don't care how many times you have measured continuity, if it was all connected correctly you wouldn't be having a problem.

[The Captain]

Ah apologies Mark. I meant I redid continuity over whole circuit, & the '3 new bits' added I meant just the new tone additions in Q. I was trying to explain Im thourough/ ALWAYS redo basic checks to rule out ANY page 1 dumbness you may be quizzical over, ie using the n/c pair of inputs, any bad solders, wrong R values etc etc.. too much info maybe.

So all as 5E3 with the added tone config: re diagnosed prob area- replaced the .022 cap, 100k grid R measures ok from tube pin, & general continuity around here all fine (all solders here checked with magnifying glass too) = still noisy.

[MWJB]

Leaving the wire from the 100K plate resistor to V1, 6 in place, and the 100K to ground from V2, 2 - remove the coupling cap from V1, 6 to V2, 2 from the board and physically mount it from one tube pin to the next, along the chassis floor. This will eliminate you picking up any noise from anywhere else with this component.

Replace V2 with any working 9 pin preamp tube (AY/AT/AX). Does the amp still "BRRR" with just one preamp tube in V2?

[The Captain]

Hi Mark. I just did the cap job direct from pin to pin- brrr still there.

And my 12AY7 solely as V2- brrr still there.

Bugger.

[MWJB]

grounding V2,2 and/or removing V2 stops the "Brrr"?

[The Captain]

grounding V2,2 and/or removing V2 stops the "Brrr"?

Yes exactly- gnding V2, 2 with tubes in- brrrr stops. Removing V2 only stops it too.

[MWJB]

If you still get the "Brr" with V1 removed, or v1 pin7 grounded, then it must be something around V1, 6 and V2. As you haven't changed anything around V2B and you have eliminated problems with the coupling cap from V1, 6 to V2, 2, I'd now look at your grid load resistor at V2,2.

Rather than run the long ground wire to your star ground at the RHS of the chassis, ground the 100K to a solder tag under one of V2's mounting nuts.

[The Captain]

If you still get the "Brr" with V1 removed, or v1 pin7 grounded, then it must be something around V1, 6 and V2. As you haven't changed anything around V2B and you have eliminated problems with the coupling cap from V1, 6 to V2, 2, I'd now look at your grid load resistor at V2,2.

Rather than run the long ground wire to your star ground at the RHS of the chassis, ground the 100K to a solder tag under one of V2's mounting nuts.

Just done this- still same (I swapped this resisitor from 470k to 100k fwiw too). Ive surely eliminated all avenues now? on a different track, I do notice valve 2 is not as 'iluminated' as the others, ie the friendly orange twinkles not as strong.. but as it works 'fine' as stock 5e3, and the voltages checked innitially here seemed in right ballpark i dont suppose this is important in context.

[MWJB]

No, the amount of glow from the heaters is rarely sign of a problem (unless they don't light up at all), even valves of the same brand and type don't always appear to glow the same.

OK, keep going through the preamp, you've eliminated V2, 2 & V1,6. Now look at V1, 7 - what resistance do you get, from middle tab to ground, on the volume pot turned when all the way down? Repeat continuity checks from V1, 1 to treble cap. Then look at the signal path from inpiut jacvks to V1,2.

I know you have done this before, but you MUST have missed something, otherwise the amp would work fine.

[The Captain]

OK, keep going through the preamp, you've eliminated V2, 2 & V1,6. Now look at V1, 7 - what resistance do you get, from middle tab to ground, on the volume pot turned when all the way down? Repeat continuity checks from V1, 1 to treble cap. Then look at the signal path from inpiut jacvks to V1,2.

I know you have done this before, but you MUST have missed something, otherwise the amp would work fine.

Hi Mark, just whittled the above checks off:

1. vol middle tab to gnd= 2.2 ohms
2. V1, 1 to treb cap (680pf)= 0.5 ohms

And continuity from top to toe on both inputs jacks (only one pair in now) as per hoffman pages. Dummy jack inserted:

1. tip to gnd on plug.. #1= 1m. #2= 135k.
2. tip to 68k junction on board.. #1= 34k. #2= 68k.
3. 68k junction to V1, 2= 0.5 ohms.

[MWJB]

Well that all seems in order. You're getting no signal from the guitar at all?

Measure the 6.8K middle resistor where it meets the bass pot tab, to ground (chassis).

[MWJB]

Have you tried installing a negative feedback loop as per the PR? Look at how the cathode at V2, 3 is wired. I suppose, in the absence of a better suggestion, that the additional gain/layout might be making the amp unstable and some NFB might be of benefit? Be aware that if you fit a NFB loop you may need to reverse the blu/brown wires at 6V6 pins 3.

[The Captain]

Have you tried installing a negative feedback loop as per the PR? Look at how the cathode at V2, 3 is wired. I suppose, in the absence of a better suggestion, that the additional gain/layout might be making the amp unstable and some NFB might be of benefit? Be aware that if you fit a NFB loop you may need to reverse the blu/brown wires at 6V6 pins 3.

No I cant say I have- I did notice the differences at pins on V2 on the PR to the 5E3 before doing the changes.. trying to figure this out & applying though as a NFB concept, & as Ive spent nearly 3 weeks trying all these simple applications without success so far, Im reluctant to say- particularly in lieu of all your time and effort to help- that Im totally done in with it now; I did subsequently go over the plans between the 2 circuits at V2 before writing this, but its just not sufficiently clear to me what with different pin links, things going to different component values, some not bypassed, and then changes to the 6V6s too etc.. it'd finally make me go completely insane if I go on; unless there is anything else I can do thats straightforward re applying this tonestack Im afraid its just totally got the better of me Mark. Really appreciate the help of course! Capt.

[MWJB]

At this point the most straightforward thing you can do is pull the tubes, drop the chassis, pack it up & send it to me. I'll either give you an appraisal of what the problem is & the cure, or for an hour's labour isolate it and rectify. Drop me a PM for my work adddress.

[The Captain]

Thats a fine idea thanks indeed- but Im gonna start afresh Mark besides as its a right dog's dinner Id be far too bashful to send what with all my tinkerings!!
So my plan now is the PR circuit using your PT (earlier breakup with PR circuit too?- not so important for now mind), the Jensen, the OT and valves (bar the 5y3) & odd bits/ flog my pine cab + chassis & recoup some £s hopefully.

Qs before I start: the PR bias circuit takes a feed from the 5U4GB's HV at pin 4 to a 100k to drop voltage etc.. as this PT is 508V, is this sufficient to use similarly? (poss Id use a lower dropping r if Im thinking right). Also is the filament's 6.3V pair, at 2.5A, ok for 1x 5u4GB, 2x 6V6- and the 2 extra ~12A*7s?

It'd REALLY clear my head to start anew; Ive learnt a heap from all this so Im confident I can plan it well- eg use all above board wiring/ do a really careful job checking each build step & solder (not that Ive ever had even one bad/ dry one)- and it'll be a right corker.
Thanks for offer Mark- rgds Capt.

[MWJB]

I'd stick with the 100k dropper from the B+ secondary, I'd adjust bias voltage farther down the line, using a trim pot instead of the grounded load resistor in the bias circuit.

If I rember right that PT has a 3A 5v winding? If so that will be fine for the 5U4 BUT... I wouldn't use a 5U4, I'd go straight for the GZ34. Fender switched to 5U4 after bumping up the B+ voltage, to correct it back down again. You don't need to shed any voltage.

2.5A for the filaments will be OK for 2x6V6 (0.9A...0.45A per tube) & 4x12A?7 (1.2A...0.3A per tube). Stock Princeton PTs are typically rated for 2A.

[The Captain]

Thats right, 5V 3A pair and the 6.3V 2.5A filament pair. Great I can crack on with this & a gz34 on the list too; just one part's bugging me (PR schemo's type hard to see).. above 6V6s on this layout, what is this circular 'terminal' component?

http://i102.photobucket.com/albums/m106/TheCaptain_02/princeton_reverb_aa1164_layout.gif

Thanks Capt

[TD_Madden]

don't know which component you are referring-to, but if it's the one on the left-center...that's the top of the can-capacitor.....

[The Captain]

Can capacitor eh.. Ive never seen the like before, I guess this is the filter capacitor? The 4 tags on the top- are these usually marked with a symbol (seems there's a triangle/ square etc on layout) on the cap top so you know what's what?

[MWJB]

Yes, the cap body is usually engraved with the legend.

I prefer to not use cap cans so I can run my grounds to where they need to go.

[The Captain]

Ok, so I need a '4x 20 multicapcan' with 4 solder lugs.. none from the usual sources from UK/ EU. Is there any capcan I could use instead? Is the reason these blasted things are used only that ~4x 20uf axials would just take up too much space?

[MWJB]

If you're using the Torres PT you will only have a B+ of 330v-ish, 450v e-caps will be fine, like the Evox Rifas from Bluebell. Use 47uf for the main filters.

Cap cans were a time/costsaver for mass produced amps, they are often a cause of hum. There is no reason for a private builder to use them unless a customer requests it to keep a vintage amp looking original (even then I still wouldn't).

[The Captain]

I dont think I'll have room Mark: I plan the BF Princeton no-verb now in a Bluebell 13.5" chassis to mount 'upright' a la 5E3 in the cab, just. I'd have to build another cab to use a 17" for eg to get a PR in, or to use 4 Evox axials- space really tight. Weber do a can-cap which the same PT I had in the 5E3 uses, but with its lower 540v HV pair (tho the bias board takes a dedicated 45v feed from the PT not pinching it off the ~GZ34's pin 4 like Im going to do), so, the torres PT being not far off @ 508v means I could use the same 4x20uf can-cap.. unless Im talking baloney of course!

I presume the Princeton Amp AA64 is just the PReverb minus the reverb- it seems to have 2 less 12A*7 tubes though. I hoped to add a MVol to the PR at a later date too, can this idea still apply to the Princeton no-verb do you think?

Any comments very welcome, Capatain

[black_labb]

I was about to say, do as Stokes said, build a BF preamp, and a dual champish power section, two tubes, with one who can be switched out for less volume. It has been done before iirc.

Bye.

Max.


why not put a vol pot on each, then you can adjust each volume to suit your needs. pump one up for overdrive, keep them both equal for a cleaner sound and mix them around a bit. why not change the tube type to get different sounds?

[Satamax]

why not put a vol pot on each, then you can adjust each volume to suit your needs. ? How would you stop them interacting with each other? :D Otherwise we would have a real nice way of quietening big multivalve amps :D

[black_labb]

How would you stop them interacting with each other? :D Otherwise we would have a real nice way of quietening big multivalve amps :D

im just looking at simple designs for myself at the moment, but my thought was to have the power tubes in paralell each with their own pre amp stage before the pot. you could have one preamp stage before the splitting of the signal. maye using a pot to adjust the gain on the first preamp stage for when there isnt any signal going into one of the signal paths. it might not be perfect, but it would be alot more adjustable in terms of sound.

i dont know much about amps, but it seems feasable to me...