I thought I create a new topic for the OR200 model (4xKT88) since I don't want to hijack those other threads..
Early 1970s model. One of the last ever made. I have tried to push it hard today (with bass and 4ohm cab) and it blew in minutes (1A fuse blew after a short loud hiss and no output since then). two 270R screens look toasted. Smells bad. Photos below.
catalin gramada suggested doubling the screens value for harder use. Any other opinions aobut it? I dont want to change the sound, but I really do like this amp for bass and it's hard not to overdrive it. List of questions:
1. What screeen resistors should I use - what resistance, what wattage? Official schematics are not known.
2. Re Cap. Asking about those two big 64+100uf caps. Can they be replaced by two 100+100uf caps? No harm?
3. What else do you suggest to change/look for
4. There are 5 test points on the amp (photo), I suppose four of them are individual bias points for each tube (?) and they have test points/pins near tubes. it says SET TO 1.4 VOLTS. So, between those points and ground? Fifth is labeled BALANCE. Is it hum balance or side balance?
Thanks
Early 1970s model. One of the last ever made. I have tried to push it hard today (with bass and 4ohm cab) and it blew in minutes (1A fuse blew after a short loud hiss and no output since then). two 270R screens look toasted. Smells bad. Photos below.
catalin gramada suggested doubling the screens value for harder use. Any other opinions aobut it? I dont want to change the sound, but I really do like this amp for bass and it's hard not to overdrive it. List of questions:
1. What screeen resistors should I use - what resistance, what wattage? Official schematics are not known.
2. Re Cap. Asking about those two big 64+100uf caps. Can they be replaced by two 100+100uf caps? No harm?
3. What else do you suggest to change/look for
4. There are 5 test points on the amp (photo), I suppose four of them are individual bias points for each tube (?) and they have test points/pins near tubes. it says SET TO 1.4 VOLTS. So, between those points and ground? Fifth is labeled BALANCE. Is it hum balance or side balance?
Thanks
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