New Thunder 1 Reverb Owner

capnjuan

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My pleasure; have you had a chance to swap the 12" speaker leads yet? Any difference?
 

Archer993

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At that point of realization I had already clipped away the reverb cap can and still haven't gotten parts delivered. Hopefully today.
I thought I could get this project off the kitchen table BEFORE my wife returns from Fl. It's going to be close...
 

capnjuan

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What about the dry signal; is it okay?
 

capnjuan

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capnjuan said:
What about the dry signal; is it okay?
Ignore this ... I forgot the dry signal uses the reverb amp too. :oops: :D
 

Archer993

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NO LUCK:

All electrolytic caps replaced except the one mounted to the reverb unit.

The regular section of the amp sound great as does the tremelo.

The difference with the reverb signal is that it no longer oscilates—it's just a white noise machine. It took several clicks on the foot switch to make it come on.

Here's a shot of the outboard caps for the reverb section.

caparray.jpg
 

capnjuan

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That's spiffy work on the caps. Below is part of the schematic; on the original, the switch positions for the FS are labeled wrong; they are corrected below. Instead of grounding out the reverb like most FSs do, this one shunts dry signal to the 6BM8 when reverb is 'off' and breaks the signal from the line amp when the reverb is 'on'. As drawn below, when the switch is in the 'up/off' position, the 6BM8 sees the dry signal and when 'down/on', the signal from the reverb 12AX7 feeds the 6BM8.

preamptoreverb.jpg


If you are getting dry signal out of the 8" speaker, it means that at least one of the reverb cap sections is good; so is the 6BM8 and the output transformer. I guess I'm saying that unless you get no signal from the 8" speaker and unless the remaining reverb cap section that feeds the 12AX7 is bad, you've proofed the power and the white noise is between the connection on the 12" speaker and the reverb side of the reverb switch. Stating the the obvious some contact cleaner on the FS ought to help ... but I don't think it's the problem.
 

Archer993

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I hit all pots and switches with contact cleaner when I first got the amp. Then again a few days ago,
There are more caps on the reverb board to change and the one on the reverb unit itself. I'll be back at it next weekend and see what happens. In the meantime, the patient is still on the table . .. .

Does anyone have a photo of their reverb board for comparison????

Thanks
 

capnjuan

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Hi Tim:
you said:
It took several clicks on the foot switch to make it come on.
and then I said:
Stating the the obvious some contact cleaner on the FS ought to help
after that said:
I hit all pots and switches with contact cleaner when I first got the amp.
Well; not to put too sharp a point on it but whatever you did didn't work; you didn't lube up the spring mechanism. Unless you've done continuity checks on the contacts, you don't know whether or not the switch makes/breaks correctly ... even when you get it to function. You can fight the switch or get another one; SPDT.

twinreverbcbs.jpg
 

Archer993

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Thanks for the photo - no missing components on mine then.
Yes, I think the switch might as well go, but I will do a test on full functionality. I'll probably jump the contacts first.

CAPACITOR VARIETY:
There are numerous "types and or makes" of capacitor in this amp. Not having the amp in front of me I believe there are 7 variations . . . and that striped chicklet one going to the bass pot is really exotic looking. I certain caps are used for power & tone but 7 variations!
 

dogman

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Calling Capnjuan, while we are on the subject. Can you tell me the value of the resistor under the green capacitor on the left at the bottom of the reverb board from the last pictures. My circuit board is like the one on the left. I smoked that one by standing on my head and putting the 2 tubes in the wrong sockets and let the smoke out of that one. Too burnt to read the rings now. Thanks in advance.
D
 

capnjuan

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dogman said:
... Can you tell me the value of the resistor under the green capacitor on the left at the bottom of the reverb board ...
It looks like 33K. Assuming it's failed open, if you have a meter and get 330K between the load side of the .0047cap and ground, then it's good and it's the 33K that's gone ... unless of course both are smoked.

reverbinput.jpg
 

dogman

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Thanks capn, too bad I'm still relying on a stable memory bank. The resistor I smoked is actually the one second one in from the right on the TOP of the picture, left picture. Looks like blk/brn/brn/silver to me from the pics. Is my eye sight gone like my memory? Thanks again in advance.
D
 

capnjuan

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dogman said:
... The resistor I smoked is actually the one second one in from the right on the TOP of the picture, left picture. Looks like blk/brn/brn/silver to me from the pics. Is my eye sight gone like my memory?
Hi DM: reading colors off web-pics can be a guessing game; too many things going on ... color attributes of the camera, original lighting, piddling with the pics in pic editor applications, out to the web, back down to earth and then how different monitors render the same colors differently ... and then there's the part about eyesight.

If you are certain about which resistor is smoked ... then I don't think it was black / brown / brown ... black is never used as the first color. What follows is part certainty and part guesswork ... I'm relying on the same funky colors too; with that out of the way, here we go.

You said '2nd in from the top'; to me, that's R #8 below. If so, that's the cathode resistor for the front / triode half of the 6BM8 ... the driver half. If that's the triode cathode resistor, it would be coded red (2) / red (2) / red (times 100) ... 22 X 100 = 2,200 = 2.2K.

dogmanresistorsb.jpg



Let's try this: 'You're wrong Juan ... you're way off ... ' Okay ... I'm posting while drinking but if it's really brown / brown in position #s 2 and 3 (we don't care about silver or gold [we do ... but not in this case, those #s are for quality and tolerance] but, I'm wrong/you're right it's brown and brown .. that would mean that the second # is a '1' multiplied by 10 leaving the resistor's possible values as 110, 210, 310, 410, 510, and so on ... but there are no resistors on the circuit board - other than the 470 ohm - that are less than 1000 ohms. I'm not saying I'm right, I'm saying the smoked resistor can't be black / brown / brown.

Get to know this; pics like this are all over the web ... print this, print another one ... but print one.

Rschart.jpg



If you don't have a meter, get one and practice with it; you can also improve the chances of my guess being right through a process of elimination .. which is all I've done here. I like to use a continuity tester; if all I want to know is which end is grounded, I can clip a lead to the chassis and find the ground end faster than I can read 0 resistance. If #8 is the 2.2K and even if it's ruined, it'll read 0 resistance between one end and ground. Anyway, #8 at 2.2K ... it's just a guess. Good luck with the amp.
 

dogman

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thanks capn, that sounds right since I smoked it after putting the tubes in the wrong sockets. I had my chart out and I couldn't get a good read on the first ring. I figured your knowledge would give me the right rating. It took me a while but I finally found the chart buried in my electrical repair manual(years of collecting workshop info from 25yrs as a car tech). Its really smoked and I'm sure it's reading open now. Either case it has to be replaced. so thanks for the info and a nice color chart.

another bit of needed info. The reverb wire from the speaker came off during shippment to me. Where exactly does this get soldered back onto the reverb tank?
Thanks as always Oh Wizard,
DM
 

capnjuan

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dogman said:
... Either case it has to be replaced. so thanks for the info and a nice color chart. If one of the remaining ends is grounded, I'm pretty sure it's the 2.2K The reverb wire from the speaker came off during shipment to me. Where exactly does this get soldered back onto the reverb tank? DM
No rca plug at the can end? :shock: uh-oh. Probably going to need a picture of whatever you have at the input. Somebody ... maybe the guy who started this thread ... his supply from the speaker terminated on the resistor/capacitor (on the can side) that were scabbed onto the tank itself; is yours like that?

Originally ... (I mean sometimes) ... there was a little tag strip mounted on the 12" speaker frame; that's where the R and C were. From there, they fed the can with a wire with an rca plug on it. You may need to take the can out ... I mean as far as I know, it doesn't get soldered. :?
 

dogman

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Capn, there is a board on the tank itself that has a wire going into the RCA jack center hole, very thin single unshielded wire(I think)will need to check to be sure when I get home. About the wire I mean. I thought this wire might be a ground wire. I was thinking the wire from the speaker may need to be soldered to the board but got a little confused when I saw the RCA jack and the wire coming off the board on the tank going inside to the springs.
I'm sure pics would help but I'm picture challenged while I'm here at work.
 

capnjuan

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dogman said:
Capn, there is a board on the tank itself that has a wire going into the RCA jack center hole, very thin single unshielded wire(I think)will need to check to be sure when I get home. About the wire I mean.
Ok: then the R and C are can-mounted.

I thought this wire might be a ground wire.
You were thinking sensibly ... often gets people in trouble.

I was thinking the wire from the speaker may need to be soldered to the board but got a little confused when I saw the RCA jack and the wire coming off the board on the tank going inside to the springs.
You were right; has to be soldered. The R and C are in series; one end goes in the tank and the other meets the supply signal from the speaker. If you have continuity from the input transducer back to the R/C, it isn't a ground. I think member archer's was like that. He's pulled his pics; I saved a bunch of them but not that one. Pics when you get a chance.
 
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