Right back to basics/ pg1 Qs.

[Sea Chief]

Check out a Weber Mini Mass attenuator.

Its $120 I dont have a budget for this, hence the building idea olddawg.

[riz]

I'm happy to see this thread take a turn toward the attenuator. I myself use one everyday(Weber Mass 150), and I'm getting the best tones I've ever had--everything you describe not being able to attain Sea Chief. Black and brown Deluxes, and a couple Valco things. My take on your voltage concerns: since I've been attenuating it, my blackface Deluxe, with it's highish ~440 plate volts, does occasionally eat a JJ6v6s output, always a screen failure. It went years on a pair of tubes before, but I wasn't turning it up as much, instead using pedals for overdrive sounds. I've upped the screen resistor to 1k... The other amps, with lower plate volts, seem fine so far. The brown Deluxe has 375v or so on it's 6v6 pair, and the Valcos run Russian wafer base 5881 cathode bias at about 365v, and those seem reliable. One of the Valcos has been on the same set of tubes, running dimed, for about 3 years of almost daily driving. Still sounds exactly the same--those tubes can take it. Hope this helps, and hope you find the love.

[Sea Chief]

Check out a Weber Mini Mass attenuator.

Well the 25w version is $95.. maybe I could stretch, but dont think 25w is enuf for a DR? & I dont think we find these weber things over here in UK much if at all.

[Sea Chief]

I'm happy to see this thread take a turn toward the attenuator. I myself use one everyday(Weber Mass 150), and I'm getting the best tones I've ever had--everything you describe not being able to attain Sea Chief. Black and brown Deluxes, and a couple Valco things. My take on your voltage concerns: since I've been attenuating it, my blackface Deluxe, with it's highish ~440 plate volts, does occasionally eat a JJ6v6s output, always a screen failure. It went years on a pair of tubes before, but I wasn't turning it up as much, instead using pedals for overdrive sounds. I've upped the screen resistor to 1k... The other amps, with lower plate volts, seem fine so far. The brown Deluxe has 375v or so on it's 6v6 pair, and the Valcos run Russian wafer base 5881 cathode bias at about 365v, and those seem reliable. One of the Valcos has been on the same set of tubes, running dimed, for about 3 years of almost daily driving. Still sounds exactly the same--those tubes can take it. Hope this helps, and hope you find the love.

After reading about your tube eating this causes concern.. thats a pair then as you have to replace 2 I guess? so what another £35 min? If I could just get my plate V down to 410v.. Id not be so concerned,, I think that makes sense?

Maybe I could try a mini mass with the 15w DOM 1st see how I go- ideal if I could find a used one but bet thats rare as hens teeth esp here.

How does the diy version compare componentwise to the mini mass anyone know whats inside these webers? Id assume an Ohmite rheostat as starters too maybe as they seem ubiquitous vg quality ones?

[DRH1958]

Ok I understand there are some who advise caution- I will see how I go.

Reading the thoughts about extra load or work on the power tubes.. is this wise then for my DR RI, considering it has high voltages? (Just to recap: its a DR RI with a hammond xfmr). Originally I read a whopping B+ of 480v with the 5AR4 Id bought ready. After advice on here to go 5U4GB, Im still very high at 440v (~normal 22mA set).

Considering a std DR, with a 5AR4 should read 410v (so 380v ish with a 5U4) Im still sort of concerned. Should I be having a word with the supplier of the xfmr? it is noted as a DR xfmr on their site. Im thinking maybe this is the reason I was offered it as a one-off a bit cheaper by the Co.

I would advise caution in light of the higher than high voltages you have. The original DR had 410v or so on the plates and a few less on the screen but having 440v to me is just plain too high.
The data sheet specs 350v plate and 315v screen. Most people today agree this can be exceeded and most of the time are. But you are exceeding it by almost 100v and very likely are more than 100v over on the screen. Do you think that you can change screen resistors? It would help to have 1k ohm, 5 watt resistors in there.
There are ways to get that voltage down with zener diodes, but if you don't feel comfortable changing the screen grid resistors, don't bother with the zener mod. You might want to contact the seller and ask why they sold you a tranny that has too high voltage. Maybe get a few pounds refunded?
I'm taking it that you have 22MA bias current? That would be as high as I would go with these voltages. That is 70%. You could go lower for a little more safety factor. Maybe 18-19mA.
There is this newer JJ. Look at the voltage rating. Limiting values: https://www.tubesandmore.com/sites/d...ationsheet.pdf Not sure if this is your solution or not, maybe not affordable or available over there? Might help though. Anybody with feedback on these?

[riz]

The Weber doesn't use Ohmite, I think they're the Chinese rheostats. Look for them on the 'bay, they're cheap.

[Sea Chief]

Right now Im defo not happy with 440v you've made me think. On suppliers site its a "DR xfmr", and some (SF) DR's have v upwards of 430v.. so I guess thats just what he's gonna say. Maybe the reason I was sold it- he tested & discarded it as OTT high, put aside for some numpty like me offering me a discount as he did 'last one' or some such BS I forget now. It was new.

Ok chaps do you think I should be having a word with supplier about the xfmr's excessive v? (IE before I venture into attenuators).

[DRH1958]

First of all, is this your amp? Look for the PR number on the back, PR239 65_deluxe_reverb_manual.pdf And why is there a replacement transformer? Who did the work?

[Sea Chief]

First of all, is this your amp? Look for the PR number on the back, PR239 [ATTACH]34764[/ATTACH] And why is there a replacement transformer? Who did the work?

Actually DRH it is a DR (RI), but no number on back. Reason- its a "Partscaster DR": Fender RI boards I bought used, new chassis & rev xfmr are also Fender RI. Other parts from known places here: Bluebell Audio (PT), Mojo (OT), Allparts (tubes, rev tank). So the back is grey chassis. Front a fine clone faceplate. And therefore not a 'replacement xfmr per se'.

Under 1/2 cost of a new DR you see. Im thinking I should have bought an RI xfmr, but chinese made put me off, price only £10 more than this undoubtadly higher quality PT made in Canada. Ive had hammond before & solid quality= trust.

(Spkr: fender oxford Twin 12" old vintage '69- alas not the similar but way better 70's DR one).

The good folks on here, some on this thread, helped me do last checks & fire her up, & advised my 5AR4 (I had all ready as thats what on the list for a DRRI) best be replaced with a 5U4 as I got whopping 478v plate v to begin with. So its known MEF beastie.

[DRH1958]

If you built it, then you should be OK with changing out the screen grid resistors to 1k ohm I would think. The screen grid is the #1 reason for failure in power tubes. Upping that to 1k will help protect your tubes better. Then proceed with the attenuator. I suppose it's up to you if you want to question the seller about the tranny. If I felt like they tried to put one over on me, I know what I would do.

[Sea Chief]

Hi DRH. Well I put it together but the board was built already (two fender pcb's, main board & 'pot board'. sorry should have made clearer: obviously s'one redid their RI as a p-to-p handwired affair, which is no doubt a better method).

Getting in ad replcacing the grids is a major exercise. Why arent they 1k as they are, to be more sturdy anyway?

Re the xfmr query: you see Im trying to evaluate whether in your opinions on here, I have indeed been either done over by way of an odd xfmr pushed my unsuspecting way (Id have thought theyre tested at factory for their HV, but remember the spiel always says +- 10% or something so if twds top of this range but just 'in' still. And, theyre made a generic xfmr & not specifically for DR's afaict IE "for a DR" added by the Co I bought from) or have to accept either they are generally much higher V (in which case would I not be Querying the Co's "for a DR" info) or as said if within the +-10% range then some will just be higher: the lower ones he likely uses for his pro builds.

All I'd do without the knowledge you guys have, is call just for him to spiel the +-10% tolerance thing, or "thats easy just put in a 5Y3", or it is "a bit of a lucky dip", or "its perfectly normal SF DR's run a high ~ 430v with a 5U4" (thing here tho is all builders do the BF circuit with the 5AR4 by default unless they specify an xfmr for an SF, surely).

Im wondering if I should ditch this PT you see, and buy the chinese (gasp) standard RI. A waste of nr £100 (need a 5AR4 as I sold orig one as had no need) + the work, but if it means using with a attenuator Im substantially safer.. then surely the only way to proceed.

[Sea Chief]

Chuck- the ohmites seem to go 25r/25w, 50/50, 100/100 etc.

Am I after a 25r/ 50w? or would a RJS50R do?

Also Ive found a weber employee page whose put up the mimimass etc schematic (the minimass seems to go 50r/50w fwiw). http://freestompboxes.org/members/so...erMiniMASS.gif Main difference it seems to your DIY one above is the "speaker voicecoil" section. Whats the idea here, and is this do-able?

[Sea Chief]

Chuck is this one correct type? RJS50R Ohmite | Mouser

[Mick Bailey]

Right now Im defo not happy with 440v you've made me think. On suppliers site its a "DR xfmr", and some (SF) DR's have v upwards of 430v.. so I guess thats just what he's gonna say. Maybe the reason I was sold it- he tested & discarded it as OTT high, put aside for some numpty like me offering me a discount as he did 'last one' or some such BS I forget now. It was new.

Ok chaps do you think I should be having a word with supplier about the xfmr's excessive v? (IE before I venture into attenuators).

I've noticed the output voltages on Hammond transformers to be on the high side. Can't recall this being a problem in the past, but on a few amps I've had to correct the voltages. Maybe the UK versions now have 'harmonised' European specs which give the correct voltage on 230v, but in the UK read high - especially on a step-up transformer. I get this quite a lot now as very few manufacturers make 240v-specific transformers, even in the UK. There are two versions of some Hammonds; the fixed primary type and 'universal' promary which have quite a few wiring options. Check which yours is, as it could be wired for 230v.

The other thing is to check the heater voltage to see if it reads 6.3v loaded.

An interesting thing is that most original Fenders sold in the UK are incorrectly configured from the factory. They're marked "UK Mains 230v" and read high anyhow. This is despite them having taps for 240v, which on some Fender drawings is shown as Australian Mains. In every case I've had to wire the UK amps for 240v to bring the voltages in line. Just 2 wires to swap.

[Sea Chief]

Good point Mick re the primaries- but alas its just got two primary side for 240v.

Here is the monkey in Q, and, as you can see its banded a "DR xfmr" here as other places (even sold in correspondence with the fender equivalent part no). Mine not bought from here, but similar "fender DR" xfmr spiel.

The wiring diagram is just below the main pic/ enlarge. Hammond 291BEX Fender Power 125P23D / 041316 UPGRADE - Tube-Town GmbH