Throwing metal film resistors in Fender amps

[tubeswell]

If its a BFDR circuit then Doug's blackface fender type amp board layout is tailor-made for that http://www.el34world.com/Hoffman/ima...TwoChannel.gif,

[Wil]

Hello,
I finally finished my build and the load of problems I expected has arrived.
First here are some pictures :




When I fire the amp up, I get a lot lot lot of hiss and a bit of motorboating. When I touch the string I have a small "tick" that makes me think it's a grounding problem or polarity problem.
On the pictures, there's not connection between reverb lug 1 and ground. That's a first mistake. Now I'll try to reverse the polarity of the input jacks. Anf if anybody has a known working schematic of how to wire the reverb and vibrato footswich with a stereo jack, that would be fine haha !
Have a nice sunday!

EDIT : The normal channel works perfectly, and is f($"ing amazing...
Regarding the vibrato channel, the board was triple checked and all the wiring is now okay. I just need a schematic for the stereo jack footswitch (for a hoffman style board wiring) and the right method for the input jacks (the normal channel is a single input).

[tubeswell]

Hello,
I finally finished my build and the load of problems I expected has arrived.
First here are some pictures :




When I fire the amp up, I get a lot lot lot of hiss and a bit of motorboating. When I touch the string I have a small "tick" that makes me think it's a grounding problem or polarity problem.
On the pictures, there's not connection between reverb lug 1 and ground. That's a first mistake. Now I'll try to reverse the polarity of the input jacks. Anf if anybody has a known working schematic of how to wire the reverb and vibrato footswich with a stereo jack, that would be fine haha !
Have a nice sunday!

The fun starts. (And the 1st thing I want to say is I'm just making some observations)

1st thing I notice is you look like you got a lot of other (blue) wires in there compared to Doug's layout.



Trying to keep the layouts as simple as possible is better for minimising unwanted noise issues.

Clustering leads is only a good idea if the leads are 'cluster-able'. Some leads aren't good companions. All wires are inductors and AC within each wire produces EMF around the wire, which can couple into other wires. With the extra leads you put in there, that may be causing some problems (maybe)?

Is the noise from grounding? - could be part of the reason (hard to see your grounding setup from the pic). How are your reverb pan send/return sockets grounded? Have you kept to a galactic grounding system (like Merlin Blencowe's article)? or a bus ground? Or a combination of the two? Grounding is fairly critical in BF amps. Several ways can 'work'. But you have to find the best way that works for you.

Does the amp make noises with the guitar cable unplugged?

Do the noises differ when you twiddle different knobs? or pull out different pre-amp tubes?

If you disconnect the NFB loop does that makes a difference?

Are the input jack tip switches making proper contact without cable jacks plugged in?

[Wil]

The fun starts. (And the 1st thing I want to say is I'm just making some observations)

1st thing I notice is you look like you got a lot of other (blue) wires in there compared to Doug's layout.

[ATTACH=CONFIG]27649[/ATTACH]

Trying to keep the layouts as simple as possible is better for minimising unwanted noise issues.

Clustering leads is only a good idea if the leads are 'cluster-able'. Some leads aren't good companions. All wires are inductors and AC within each wire produces EMF around the wire, which can couple into other wires. With the extra leads you put in there, that may be causing some problems (maybe)?

Is the noise from grounding? - could be part of the reason (hard to see your grounding setup from the pic). How are your reverb pan send/return sockets grounded? Have you kept to a galactic grounding system (like Merlin Blencowe's article)? or a bus ground? Or a combination of the two? Grounding is fairly critical in BF amps. Several ways can 'work'. But you have to find the best way that works for you.

Does the amp make noises with the guitar cable unplugged?

Do the noises differ when you twiddle different knobs? or pull out different pre-amp tubes?

If you disconnect the NFB loop does that makes a difference?

Are the input jack tip switches making proper contact without cable jacks plugged in?

Thanks for the flash fast answer again!
I believe my input jack layout is not right so I will start by rewiring like the DRRI layout.
My second problem is the stereo footswitch jack. Don't really now how to wire this because the DRRI has extra component.
The blue wires are from the filter caps board.
The normal channel is silent, which makes me hope the vibrato channel can be too!

[Wil]

This is the first and last time I'll say that kind of things on this forum but :
Holy SHIT this amp sounds absolutely GORGEOUS ! The sound is really amazing. AMAZING ! Best amp I've ever played for sure.
I'd really like to thank you all for your help, it would have been impossible for me to achieve this without you MEF members ! That must be the beauty of the internet.

tubeswell
soundmasterg
Alf
Alan0354
catstrat
soundguruman
Frus
J M Fahey
Gingertube
Mick Bailey
kg
Tom Phillips
Tedmich
R.G
Jazz P Bass
Enzo
jcmjmp
Mars Amp Repair
Mhuss

You're all part of that amp. Thank you.
I will make a video soon to show you how it sounds and until the next problem, I'll leave you in peace and won't require you help, haha :-)

[Wil]

This is the first and last time I'll say that kind of things on this forum but :
Holy SHIT this amp sounds absolutely GORGEOUS ! The sound is really amazing. AMAZING ! Best amp I've ever played for sure.
I'd really like to thank you all for your help, it would have been impossible for me to achieve this without you MEF members ! That must be the beauty of the internet.

tubeswell
soundmasterg
Alf
Alan0354
catstrat
soundguruman
Frus
J M Fahey
Gingertube
Mick Bailey
kg
Tom Phillips
Tedmich
R.G
Jazz P Bass
Enzo
jcmjmp
Mars Amp Repair
Mhuss

You're all part of that amp. Thank you.
I will make a video soon to show you how it sounds and until the next problem, I'll leave you in peace and won't require you help, haha :-)

[tubeswell]

Glad you managed to sort it

[Alex R]

FWIW using those 22uF caps is "vintage compatible", whatever that means , since typical electrolytic capacitor tolerance in the old days was -30/+50% , so anything between *real* 11uF and 24uF is solidly within Leo´s specs.

By FAR the most important "vintage" parameter is using well worn 50 y.o. speakers and I´m constantly amazed by people obsessed with irrelevant parameters such as capacitor colour and ignoring the most important parameter of them all.

+1. When customers ask if I can make their HRDL sound less harsh, I recommend buying an old ceramic 12" someone is selling because they fitted something fashionable instead and put that in the HRDL, so the old speaker goes on ebay for £15 or something. Instant 'vintage tone'; I have some very happy customers because it really makes a difference. Same story with the AC30CC, or anything with new celestion blues, they sound too sharp and toppy till they are well played in, but alas played in celestion blues aint so cheap as old Fender ceramics.

[Wil]

Strange and annoying thing is that I still can't use Tung Sol 6v6...
The JJs run good but I love the TS 6V6 and want to use them in that Deluxe.
At 17mA per tube, the JJ's plate voltage is around 415V. This is not that much is it ?
With the bias pot set the same, the TS current is at 22mA and they heat like crazy... I did not even try to play, I'm sure they would have blown up. I noticed that, with the TS, the current was oscillating a lot (+- 1.5mA, could be stable for a while) which makes me think it could the a "screen-related" problem.
I already had the problem with the stock DRRI, so the transformers might also play a part in that problem.
Should I try a 5u4 instead of the gz34 to lower the b+, or the zener diodes mod ?
Could the screen voltage kill power tubes ?

Hahah, and still there are problems with the annoying boy's amp.

[tubeswell]

At 17mA per tube, the JJ's plate voltage is around 415V.

Nuthin' for a JJ6V6S

With the bias pot set the same, the TS current is at 22mA and they heat like crazy... I did not even try to play, I'm sure they would have blown up.

But what was the plate voltage? (Plate voltage x plate current = plate dissipation)

Should I try a 5u4 instead of the gz34 to lower the b+

If your 5V winding is rated for 3A draw, then why not?

Could the screen voltage kill power tubes ?

More like screen dissipation. Thats why using an appropriate Rg2 resistor at each screen grid pin can be a good idea

[Wil]

Nuthin' for a JJ6V6S



But what was the plate voltage? (Plate voltage x plate current = plate dissipation)



If your 5V winding is rated for 3A draw, then why not?



More like screen dissipation. Thats why using an appropriate Rg2 resistor at each screen grid pin can be a good idea

Can bigger screen grid resistors (1k5 5W) allow me to use the TS 6v6?

[tubeswell]

470R 1W for Rg2 on a 6V6 should be sufficient.

Otherwise you could lower your screen voltage by going to a 5k screen supply dropper. That will drop the screens to about 50-60V below the plates like a mid-50s fender.

But what was the plate current/plate voltage like for the TS?

[Wil]

470R 1W for Rg2 on a 6V6 should be sufficient.

Otherwise you could lower your screen voltage by going to a 5k screen supply dropper. That will drop the screens to about 50-60V below the plates like a mid-50s fender.

But what was the plate current/plate voltage like for the TS?

JJ's :
V7=V8
Pin 2 : 2.2VAC
Pin 3 : 394V
Pin 4 : 394V
Pin 5 : -27V
Pin 7 : 2.2VAC
Pin 8 : ~0V
Biased at V7 19.5mA, V8 19.2mA.

Tung Sols:
Pin 2 : V7=V8=2.2VAC
Pin 3 : V7 392V, V8 391V
Pin 4 : V7 390V, V8 389V
Pin 5 : V7=V8=-30V
Pin 7=Pin2
Pin 8 : ~0V
Bias : V7 8.6mA, V8 25mA.

This comes from another thread where I expose how my amp just burn every TS 6V6 I put in there haha.
When I have the time, I'll put 1k5 screen grid resistors and 470ohm grid stoppers to see what it does!

[tubeswell]

JJ's :
V7=V8
Pin 2 : 2.2VAC
...
Pin 7 : 2.2VAC


Tung Sols:
Pin 2 : V7=V8=2.2VAC
...
...
Pin 7=Pin2

Surely any problem you are having with the sound is insufficient heater voltage. At the plate and screen voltages you report, those tubes should have no difficulty operating.

I'm a bit suspicious at seeing 8.6mA on one side and 25mA on the other side for the TS. Have you tried a different set of TS?

[Wil]

Surely any problem you are having with the sound is insufficient heater voltage. At the plate and screen voltages you report, those tubes should have no difficulty operating.

I'm a bit suspicious at seeing 8.6mA on one side and 25mA on the other side for the TS. Have you tried a different set of TS?

I believe the heater voltage measurements are wrong because of my multimeter.
But yes, the amp blew 2 sets of tung sols up.

I put 1k5 screen grid resistors instead of 470ohm and 470ohm for grid stoppers.
Plate is now 386VDC, screen 381/382VDC and current 0.027mA. I still want the screen voltage lower.

Here's how they look after 1 min of warm up (stand by on):


This is red plating to me...
Notice the blue "gaz wave" at the base of the tube.