Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: jewishjay on September 26, 2021, 09:09:59 pm
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70s Silverface Deluxe Reverb everything works as it should except no tremolo and no reverb. The tremolo bulb is blinking, but there's no tremolo. The reverb tank seems ok, there's resistance across each little coil and the foot switch is working correctly, but there's no reverb. Good sound in both jacks in both channels and all the tone controls work, but both of the effects are dead. I've tried swapping tubes all around. Here's the voltages to ground (parenthesis approx pulses when trem is activated)
V1
1. 216
2. 0
3. 1.6
6. 211
7. 0
8. 1.6
V2
1. 229
2. 0
3. 1.5
6. 232
7. 0
8. 1.6
V3
1&6. 400
2&7. 0.2
3&8. 5.7
V4
1. 219
2. 0
3&8. 1.7
6. 215
7. 0
V5
1. 408 (180)
2. -44 (0.1)
3. 0 (2.3)
6. 360 (330)
7. -43 (1.8)
8. 0.1 (17)
V6
1. 286
2. 42
3&8. 54
6. 277
7. 43
V7
3. 415
4. 418
5. -36
V8
3. 416
4. 412
5. -36
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If the footswitch isn't turning the trem on/off then most likely the LDR part of the trem roach is kaput. Suggest you install a new opto-coupler (trem roach).
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OK, I'm having trouble figuring out what would be common to both the trem and the reverb portion of the circuit, while leaving the remainder of the amp operating normally.
Are you using a pedal controller?
Did both the trem/vib and the reverb fail at the same time? What was happening when the failures occurred?
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Did both the trem/vib and the reverb fail at the same time? What was happening when the failures occurred?
Craigslist special. Came to me an absolute wreck. Someone replaced the PT but wired it all wrong. Sloppy workmanship and cold solder joints everywhere. So I dont know any history. I just know that I got it running, and checked the bias....and now the last problem (or problems) are the Verb and Trem. No effect. Good sound, but the verb and trem dont effect the sound.
Those voltages all look good to everyone?
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Those voltages all look good to everyone?
The voltages look good but V5 was measured with the trem switched OFF.
It would be nice to turn the tremolo ON, and see that Pins 2 & 7 drop to 0v while Pins 3 & 8 rise to 1-2v. When this happens, Pins 1 & 6 will drop somewhat in d.c. voltage.
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It would be nice to turn the tremolo ON, and see that Pins 2 & 7 drop to 0v while Pins 3 & 8 rise to 1-2v. When this happens, Pins 1 & 6 will drop somewhat in d.c. voltage.
Please see the numbers in (parenthesis)
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The roach bug is blinking. There are only two components between a blinking roach and tremolo sound... The LDR half of the roach and the INTENSITY pot. It's rarely the pot. :wink:
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REVERB FIXED. the transducers inside the tank were good, just loose and slopping around. I wedged a very thin shim to tighten the coils against the laminations. and the reverb works now.
I'll order an LDR which will most likely fix the trem...