Everything You Ever Wanted to Know: Pictures & Diagrams

[Tdale]

I wonder if HAD is a registrated user here.... It's probably not that unlikely...

tommy

[ayan]

B+ of 440V on the plates is very consistent with that particular model number of TR power transformer. I've worked on more twins than I care to think about. You may gain an extra 5 to 10 volts of so with new caps, but that's about it. As the caps become formed it always seems to drop back to 440V anyway !!

Interesting information, I somehow was under the impression that one would expect to see on the order of 460VDC instead.

* * *

One note to all: the purpose of this thread is to make available to you information that I know you will enjoy, appreciate and learn from. The copyright of the pictures is mine and I have made it clear that I have no objections to you doing with them as you please. I ask that we please keep a positive attitude, good karma and stick to the the subject of interest. To me, that does not include speculation about whether anyone may either throw a party or a fit when they see the pictures, or who is and isn't a member of this forum. I ask that you please try to accommodate my request, and there is no need to respond to this with a follow up to my post, please.

Thanks,

Gil

['67_Plexi]

Sorry, no harm meant or intended.

['67_Plexi]

It's interesting to see that on the relays there are two pins dedicated to driving the LEDs through the 1k resistors. I should try that, it means you don't need to worry about voltage drops in the coil circuit. Give it 12V regulated and you're good to go.

I am interested to know if there was any noticable pop on channel changing.

[ayan]

It's interesting to see that on the relays there are two pins dedicated to driving the LEDs through the 1k resistors. I should try that, it means you don't need to worry about voltage drops in the coil circuit. Give it 12V regulated and you're good to go.

I am interested to know if there was any noticable pop on channel changing.

Plexi, also note that there is a 5th pin running an isolated ground from the location of the voltage regulator. I have seen some folks using 4-pin connectors and using the chassis ground connection at the XLR instead, which obviously does not result in ground isolation.

As for the channel switching, there is no noticeable popping sound on that amp. It does use a single overall master volume, though, which is not the reported culprit among those who have build amps and have complained about noisy relay switching.

Gil

['67_Plexi]

Good point, the HRM is the one known for it's popping tendencies, as I very well know. It's not horrendous, but is noticeable in a non-playing environment.

BTW, it really is awesome you posted this info. It's a great education resource for a lot of people.

[Pete]

B+ of 440V on the plates is very consistent with that particular model number of TR power transformer.

I have this transformer in my build. I'm getting 444v, sound (of the amp) is typical (i.e. pretty darm good).
P

[mlp-mx6]

Gil,

Are both of the "snubber" caps 270pF? Seems like I can see the V2A one, but not the V2B one. And no mention of them in the layout drawing that I saw.

Also - is there a single shot of all the innards? (just hoping)

Interesting also the values for the pots. I don't recall seeing a non-HRM guideline that has 250KL as the Drive pot. Maybe I'm just confused...

Thanks again!
Michael

[ayan]

Gil,

Are both of the "snubber" caps 270pF? Seems like I can see the V2A one, but not the V2B one. And no mention of them in the layout drawing that I saw.

Also - is there a single shot of all the innards? (just hoping)

Interesting also the values for the pots. I don't recall seeing a non-HRM guideline that has 250KL as the Drive pot. Maybe I'm just confused...

Thanks again!
Michael

1. Yes, both snubbers are the same value.

2. Not my layout, but it's good to have over a hundred pictures to help clarify any doubts one might have after seeing Billy's notes, no?

3. I have no additional pictures.

4. Ditto on the mix'n match pot thing. Seems like a transitional amp that eventually led to the 90s design.

Gil

[Tdale]

My speculations about HAD being a member here did not have anything to do with the posting of these pictures, it was just a general speculation...

Tommy

[pazzo63]

hi, nice pictures ,i m sure that is a nice sounding amp.this is a amp very fender ispired ,but very different from the later ods where have different values of plates and cathodes, power supply, bias ecc.i think it s a one of a kind amp,and probably truely a transitional amp like sweet Mr Ayan wrote.would be nice to see pictures of how this amp has been modded from the GREAT Mr Dumble later on...also would be nice to see pictures of a more recent amps,to compare with older amps,and i m sure that some members have some and show to everybody the GREATNESS of the original builder .I ve read that the MAN is not making ods anymore,so we would not STEAL NOTHING from HIM(i apologize for my english). Dave

[llemtt]

thx Gil

this is a terrific bundle of information to me, it confirms lots of hypo gathered around from other sources during last 8 years.

There are also new things, I see a resistor and a cap between pre-out and power-in jacks, what's that? Does it works like a "parallel" loop?

teo

[ayan]

thx Gil

this is a terrific bundle of information to me, it confirms lots of hypo gathered around from other sources during last 8 years.

There are also new things, I see a resistor and a cap between pre-out and power-in jacks, what's that? Does it works like a "parallel" loop?

teo

Now that's a good question, Teo. As it were, if you look carefully you will see that the little network you decribe is wired to the switching lug in the return loop jack. So, once you plug something into that jack, the network is disconnected. We tried it by bypassing the loop with a short patch cord and, as expected, found that it enhances the brightness ever so slightly.

Gil

[Pete]

I see a resistor and a cap between pre-out and power-in jacks, what's that? Does it works like a "parallel" loop?

I too am very curious about this, I have seen it in pictures of other amps but never any discussion of it.
It looks like 220K bypassed with 250pf, connected to the jacks in such a way that it is normally in series in the signal and bypassed when a plug is in the return jack. This analysis could be erroneous.

Anyway, much thanks to Gil, I have learned quite a lot in the last few days while combining views of the pics with soldering and playing.

Pete

[tonelab2]

HAD certainly liked those 22meg resistors.
Any idea what the one on the treble pot and tone boost board are for?