Univox U305R schematics
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Univox U305R schematics
Have had this amp for many years but it needs some work now. My tech needs the schematics. Anyone here have a copy that can be shared with me. Thanks in advance.
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Stevem
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Re: Univox U305R schematics
I got mine some 25 years ago and then in darn near what seemed over night it developed several very noisy ( hiss) plate load resistors.
Since then I have fixed two more amps with that same issue, so while your amp is in the techs hands I would have him change out all of the 1/2 watt plate load resistors that are in the audio stream.
Where talking not even 3 bucks in parts.
Also the oil type coupling caps used in these amps which sound great fail very often, especially the .01 caps, so you may want them replaced as a preventative measure if there already not part of the problem with the amp now.
The one .02uf and the two .01uf caps in the Tremolo circuit fail also which causes weak or no Tremolo.
The tube sockets are pretty cheap / bad in these amps also and can make for a lot of intermittent cut outs and crackling sounds.
Since your talking the amp in likely for the normal power supply filter and electrolytic replacement just do it all in one shot if you can afford the added labor.
These amps sound great with there original Jensen speakers if still in there and the amps 18 watts of clean power make it a tad louder then a Deluxe reverb.
Since these amps only have a tone on each channel if you play both single coil and humbuckers thru the amp you may want the tech to make mods such that one channel is suited for one pickup type and the other channel set up for the other.
Lastly, the 6AN8 tubes used to drive the reverb pan are getting hard to come by, so if yours test on the weak side I would track down two of them now so you have a spare!
Since then I have fixed two more amps with that same issue, so while your amp is in the techs hands I would have him change out all of the 1/2 watt plate load resistors that are in the audio stream.
Where talking not even 3 bucks in parts.
Also the oil type coupling caps used in these amps which sound great fail very often, especially the .01 caps, so you may want them replaced as a preventative measure if there already not part of the problem with the amp now.
The one .02uf and the two .01uf caps in the Tremolo circuit fail also which causes weak or no Tremolo.
The tube sockets are pretty cheap / bad in these amps also and can make for a lot of intermittent cut outs and crackling sounds.
Since your talking the amp in likely for the normal power supply filter and electrolytic replacement just do it all in one shot if you can afford the added labor.
These amps sound great with there original Jensen speakers if still in there and the amps 18 watts of clean power make it a tad louder then a Deluxe reverb.
Since these amps only have a tone on each channel if you play both single coil and humbuckers thru the amp you may want the tech to make mods such that one channel is suited for one pickup type and the other channel set up for the other.
Lastly, the 6AN8 tubes used to drive the reverb pan are getting hard to come by, so if yours test on the weak side I would track down two of them now so you have a spare!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
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Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Univox U305R schematics
Many thanks sluckey and Stevem for the schematic and the advice. I've had mine since 1967 and it has been great. Just needs some TLC.