| Author | Message | ||
     Ian Azrikan (inertian) Username: inertian Registered: 10-2013 |
Just recapped and set the bias on a friends '78 112 Sixty-Five, sounds great except the Reverb is weak. It is present throughout the Reverb controls' range, but even at 10 is not very deep sounding. It was like this before the recap, was hoping that would help. Has original correct tank, and I tried another known good identical tank, no difference. Is there something in the circuit I can check to fix this? Seem to recall a post where there was a particular capacitor that if changed, improves the reverb. Thanks. | ||
| Lars Verholt (lmv) Username: lmv Registered: 11-2009 |
Silly question - have you tried reversing the wires to/from the tank? If the goezinna is in the goezoutta (technical terms taught to me by a tech friend of Italian decsent) it would yield the exact symptom you are describing. Sincerely, Lars Verholt | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
WE used to use gozinta and comesouta-same procedure. Like Lars said, the input and output impedences are totally different and can drastically affect the sound if reversed. | ||
| Bill Moore (bill_moore) Username: bill_moore Registered: 03-2013 |
It's great to learn new technical terms! | ||
| Ian Azrikan (inertian) Username: inertian Registered: 10-2013 |
Tried both tanks with wires both ways. No difference. Thought I read that the impedances are close enough that it actually can work either way. Gonna test the cables, suppose they can go bad. Otherwise, are there ICs I can swap or other components to check? BTW, am familiar with gozinta/gozouta from my years in IT system design... | ||
| Ian Azrikan (inertian) Username: inertian Registered: 10-2013 |
Update: - Tried different cables, no difference. - Checked resistors around Reverb jacks, all in spec. - Ran an RCA cable between In and Out Reverb jacks, Reverb control acts as Volume control as expected (feeds back when turned up). No ICs on this early (GD-1) board, is there a cap or caps that impact Reverb? | ||
| Ian Azrikan (inertian) Username: inertian Registered: 10-2013 |
Did some more research, discovered you can move the LM307Hs around (duh, I thought they were soldered in place). Sure enough, swapping #4 and #5 seems to have strengthened the Reverb sufficiently. Still not in Fender Reverb territory, but a marked improvement. Also seems that the amp is quieter at idle overall, can keep the Master Volume at 10 and use the Channel volume with a totally acceptable noise floor (hiss or "blow"). And the Bright and Deep switches seem more pronounced. I'm calling this one done... Thanks. Don't seem to have any ill effects elsewhere in the amp. | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
The LM307's are kind of hard to find, if that's your problem. There were a few around here last year or so but don't know any more. You might look at the discussions about the brown dog adapters and more modern IC's. It may help. Mike. | ||
| Ian Azrikan (inertian) Username: inertian Registered: 10-2013 |
Fortunately my friend who owns this amp doesn't use Reverb much if at all. But since I had the amp open for the recap, why not get it all working? The amp really sounds great now, reminds me of why I liked my old 210 Sixty-Five so much (and how dumb I was to sell it). |