| Author | Message | ||
     Brad Gregory (bdgregory) Username: bdgregory Registered: 07-2010 |
A guy I know has this RD-100 head and the Reverb stopped working. I ran the diagnostic procedure I found on this site and with the cable connected between the 2 RCA connectors there is a high pitched squeal when the reverb volume is turned up. I assume this indicates a problem in the reverb circuit. I have a couple of questions I hope someone can help with: 1) The reverb tank appears to be non-original. It's a very big tank - almost 17" long x 4" wide. numbers stamped on it are 1122-6850, and 984-003365. There is no brand name. Is it likely that this tank could cause one of the op amps to fault? 2) I'm trying to diagnose the problem and while I have the schematic, I don't have a circuit layout, there are no markings on the board, and the components don't appear to be the same as what the schematic indicates. Net net - I can't pin point the Reverb circuit on the board. Can anyone help here? | ||
| Lars Verholt (lmv) Username: lmv Registered: 11-2009 |
The RD-100 came in three different (at least) versions, so you may have a different schematic compared to the actual amp. Have you tried feeding signal to the reverb return RCA jack from, say, an mp3 player? If that works (it won't be hi-fi of course) next step is to pull signal from the reverb send RCA jack and feed it to another amp (stereo, computah). This signal will be pretty strong so don't turn up the volume control too high. Sincerely Lars Verholt www.captain-foldback.com | ||
| Brad Gregory (bdgregory) Username: bdgregory Registered: 07-2010 |
thanks, I have only found 2 different versions of the board. Neither appears to match though one of them is using the correct op amps. Also, the diagnostic I ran essentially performs the routine you suggest, though what you suggest may help pinpoint if the issue is with the output or return if not both. | ||
| Brad Gregory (bdgregory) Username: bdgregory Registered: 07-2010 |
thanks again for your assistance Lars - I finally broke the code. The correct schematic was the last one - with 6L6 tubes . . . and it helps if you're looking at the correct part of the board when you're trying to match up to the schematic. It turns out that the opamp (TL072) module needed to be replaced, and a lead wire to the transformer inside the tank had broken off and needed to be resoldered. I assume that the broken wire may have shorted causing the problem with the opamp. finally, all is well. |