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Late 1960s Fender Deluxe Reverb Issues

x3workshop said:
This doesn't look modded to me and this iteration may have had a slightly different cap setup. Wasn't uncommon.

Cademan maybe onto something regarding a bad tube or fried resistor. Could even be a bad coupling cap.
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Well The reason why I said it looks like it may have been modded is because there are 2 newer carbon film resistors in the amp and then one of the capacitors has a funky looking "repair job" where it looks like someone may or may not of replaced a resistor and instead of inserting the leads into the eyelets they just tied the resistor leads to the capacitor... Take a closer look at photo numbers 2 and 3 to see what I mean by this amp looks like it was modded.
 
I've only worked on a couple of guitar amps - a Fender Champ and an old Silvertone so my knowledge is limited there.
 
Power transformer is black. Output transformer is the silver cased one. the middle transformer could be a choke but where does it connect to?
If you are hearing a thump and the 6V6 tubes have the blue glow when you throw the standby switch, I would say that the output and 6V6 tubes are working and there is another problem we still have yet to find. Basically it sounds like the amp output portion is working. Preamp and inputs are now in the suspect lineup.

Do you know how to inject a line level signal into the 12AX7 AF amp/phase inverter tube? This would eliminate everything right before the output.
 
cademan said:
Power transformer is black. Output transformer is the silver cased one. the middle transformer could be a choke but where does it connect to?
If you are hearing a thump and the 6V6 tubes have the blue glow when you throw the standby switch, I would say that the output and 6V6 tubes are working and there is another problem we still have yet to find. Basically it sounds like the amp output portion is working. Preamp and inputs are now in the suspect lineup.

Do you know how to inject a line level signal into the 12AX7 AF amp/phase inverter tube? This would eliminate everything right before the output.
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No I don't know how to inject line level audio into the 12AX7 tube, All I have is a Portable CD Player and that's it, I don't have access to a signal generator or a 'scope.

And I'm assuming you mean that the larger of the two silver transformer things is the output transformer, and the smaller one is the one you think is a choke? What about the newer looking transformer looking thing, which seems to be not original?
 
Don't need a scope or generator. Just take a signal out from your cd player using either the left or right channel output. Take the (let's say the left channel) positive and connect it to pin #2 of the 12AX7 tube right next to the 6V6 tubes and take the negative side and ground it to the chassis.

What you are doing here is making sure the amplifier stage is working. You will have no volume control from the Fender controls when doing it this way so make sure the volume control is turned down on your cd player before checking. This connection basically makes your Fender a straight power amp only. If you do this and it just blasts, then you will know it is a preamp problem.
 
cademan said:
Don't need a scope or generator. Just take a signal out from your cd player using either the left or right channel output. Take the (let's say the left channel) positive and connect it to pin #2 of the 12AX7 tube right next to the 6V6 tubes and take the negative side and ground it to the chassis.

What you are doing here is making sure the amplifier stage is working. You will have no volume control from the Fender controls when doing it this way so make sure the volume control is turned down on your cd player before checking. This connection basically makes your Fender a straight power amp only. If you do this and it just blasts, then you will know it is a preamp problem.
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OK I think I can do that, I have some of those cords that were used to link together a stack unit of amps (I can't remember what my friend who gave them to me called them its just small gauge purple wire wired to mono 1/4" jacks.) anyways would that work?
 
cademan said:
Yup! :thumbsup:
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Well I tried injecting noise at pin 2 of the 12AX7 and I didn't get any audio out of the speaker (although I was using the headphone jack on my piano with the volume turned half way up) and nothing, so I'm guessing its something with the power amp and the preamp stage, of course I may have been doing it wrong too, because when I touched pin two with the positive lead of the jack there was a little neon bulb of some sort in the circuit that would glow and the speaker made crackling noises, and I didn't notice those neon bulbs glowing before and the speaker never made any crackling noises before...
 
Did you verify the speaker works OK? Disconnect it and play something through it from a different amp or receiver.

I worked on a Fender Bassman awhile back and learned at AK that there were different versions. Would not be surprising here. Usually there are ways to tell - serial numbers, trim colors, etc. But it sounds like yours was repaired rather than built different from the schematic you have.

Lordy, replace those old cardboard electrolytics before you burn down the neighborhood.

Figure out what that newer transformer is connected to and verify its role by looking at the schematic. What is that part supposed to be, and does the replacement work OK in that role? That will be the question.

Also possible you have a bad capacitor in the signal path, failed open so no signal is passing. They say these old Fenders are more prized by some if the caps are original, but if it has those Bumblebees or the blue plastic encased ones, some are bound to be bad.
 
toxcrusadr said:
Did you verify the speaker works OK? Disconnect it and play something through it from a different amp or receiver.

I worked on a Fender Bassman awhile back and learned at AK that there were different versions. Would not be surprising here. Usually there are ways to tell - serial numbers, trim colors, etc. But it sounds like yours was repaired rather than built different from the schematic you have.

Lordy, replace those old cardboard electrolytics before you burn down the neighborhood.

Figure out what that newer transformer is connected to and verify its role by looking at the schematic. What is that part supposed to be, and does the replacement work OK in that role? That will be the question.

Also possible you have a bad capacitor in the signal path, failed open so no signal is passing. They say these old Fenders are more prized by some if the caps are original, but if it has those Bumblebees or the blue plastic encased ones, some are bound to be bad.
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It surprisingly enough has all mylar coupling caps in it, black and red colored ones, the electrolytics on the other hand are mostly all original Mallory electrolytics (but it seems that there are a couple of them missing from the circuit) and a couple of really bad repairs done, also it seems that from what I've seen of pictures of other similar Fender Deluxe Reverb Amps on the internet there was supposed to be a choke of some sort where that new one is sitting currently on this one, but I think at some point in time the original one failed and they replaced it with a modern replacement, but whether or not its wired up properly or is doing its job properly (was a proper replacement or not) is another thing. also a couple of the resistors in this thing look like they've already been replaced at some point in time but it was very poorly done. So anyways it seems that this thing is just going to need to be somehow brought back to stock by undoing all of the mods that were done to this amp (and all of the poor shotty repairs) I also noticed that one of the power supply caps was already replaced in this thing because this thing is supposed to have 5 16 MFD 450V power supply filter caps in the filter cap circuit but instead it has only 4 16 MFD 450V electrolytic caps and 1 20 MFD 500V cap in the circuit. What I would like to know is what would one gain by removing two of the 7 25 MFD 25 V electrolytics from the main turret board? Or maybe was it more like whoever repaired this amp last was sloppy and forgot to install them and that's why this amp isn't working right?

And yes the speaker inside the amp is good yet, I hooked it up to the headphone jack on my old Kenwood amplifier in my basement and sound came out of it, so the speaker isn't to blame in this case.
 
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cademan said:
The standby switch just cuts off the B+ coming from the 5U4 tube. I think those standby switches do more bad than good especially when slamming the tubes with B+ when the tubes have already been warmed up.

Some pics maybe and we can probably show you which transformers are which. I also forgot to mention that my Fender had a non working vibrato which turned out to be one of the 12AX7 tubes was half lit. The heater in 1/2 of it was burned out. In a dark room, look at the 12AT7 and 12AX7 tubes to make sure both halves are lit.

Is there any sound, hum or crackle when your ear is right up to the speaker?

The power resistors are usually square brick looking things attached from one of the pins of the 5U4 tube but can also be color coded high watt resistors.
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There is a school of thought that claims "cathode stripping" is the reason to let it warm up first. This actually seemed to be demonstrated in CRT TVs in the past. In fact some delayed turning on the video to try to stop this. But these things had really small cathodes and huge plate dissipation.

But then "hot swittching", which is a ham/CB radio term refers to when that relay or whatever clicks when you key the mic. Rectifier tube datasheets have stated deration factors for this "hot switching" when used in such transmitters.

Whose tubes last longer ? We will never know. The duty cycle, current, power and voltage levels are so different it is like comparing apples to elk.

Actually I fixed a 1,000 watt linear amp that used a vibrator.
 
Those old films caps might be fine. I'd replace the electrolytics and get it back to stock as much as possible and then worry about the coupling caps. Certainly replacing a 16 with a 20 is not going to make it not work, but eliminating several is questionable!

Do you have a link to a schematic?
 
toxcrusadr said:
Those old films caps might be fine. I'd replace the electrolytics and get it back to stock as much as possible and then worry about the coupling caps. Certainly replacing a 16 with a 20 is not going to make it not work, but eliminating several is questionable!

Do you have a link to a schematic?
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Yes I do have a schematic and a layout chart as well, of which I will upload both.deluxe_reverb_ab763_schem.gif deluxe_reverb_aa763_layout.gif
 
Check the items circled in red. Sorry as I thought the 12AX7 was the AF amp/phase inverter but it is actually (according to the schematic) the 12AT7 tube so try inputting a signal at pin #2 of the 12AT7 tube (circled in yellow)deluxe_reverb_ab763_schem.jpg .
 
Capt, I would recommend you join the Hoffman forum -- http://el34world.com/Forum/index.php -- and start a thread there similar to this one. It's a guitar amp-specific site and the guys that hang out there are very experienced amp techs and builders who know Fender amps backwards and forwards. They will not only be able to help with diagnosing the no sound issue , but also advise you on the repairs/mods that have been done and whether they need to be revised, and what else should be done to keep this very nice amp working for your friend's son (who really lucked out on this deal!) . (BTW, this referral to another forum should not be construed as any kind of a knock on AK).
 
drew_t said:
Capt, I would recommend you join the Hoffman forum -- http://el34world.com/Forum/index.php -- and start a thread there similar to this one. It's a guitar amp-specific site and the guys that hang out there are very experienced amp techs and builders who know Fender amps backwards and forwards. They will not only be able to help with diagnosing the no sound issue , but also advise you on the repairs/mods that have been done and whether they need to be revised, and what else should be done to keep this very nice amp working for your friend's son (who really lucked out on this deal!) . (BTW, this referral to another forum should not be construed as any kind of a knock on AK).
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This advice is the best. I actually went to that forum to sort out a bad tremelo circuit in my Silvertone. They are very helpful!
 
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