Hi Folks;
The Latest project is a Traynor Beta 800, built just south of me, in Toronto. I almost thought I got the deal of the century; I replaced the line cord plug, and the amp seems to work perfectly!.....no DC on the outputs and a clean sine wave with my 'sacrificial' speaker.
The dummy load would prove otherwise. Chan A develops 42.7 V RMS. Chan B gets to 19 Volts, then colapses to spikes and oscillations. When the amp is powered down for 30 seconds, it seems to 'heal' itself, until the output again reaches about 19 V.
There is a schematic on the inside cover but it is in rough shape. I found a scan version of this schematic, on-line but just wondering if anyone has a service manual?
I've been warned about this amp, by knowledgeable folks here at diyaudio, but I hate to give up without a fight!
The Latest project is a Traynor Beta 800, built just south of me, in Toronto. I almost thought I got the deal of the century; I replaced the line cord plug, and the amp seems to work perfectly!.....no DC on the outputs and a clean sine wave with my 'sacrificial' speaker.
The dummy load would prove otherwise. Chan A develops 42.7 V RMS. Chan B gets to 19 Volts, then colapses to spikes and oscillations. When the amp is powered down for 30 seconds, it seems to 'heal' itself, until the output again reaches about 19 V.
There is a schematic on the inside cover but it is in rough shape. I found a scan version of this schematic, on-line but just wondering if anyone has a service manual?
I've been warned about this amp, by knowledgeable folks here at diyaudio, but I hate to give up without a fight!
Attachments
Step 1 would be, IMHO, so find some way to get the heat sink out and mount it upright so you can access both sides of the bad board. One amp I did, the right and left boards would move mechanically and the wire harness would stretch so the daughter board could be on top. Good design, practical thinking by the packaging engineer.
Then I would look at the input of the VAS transistor and see if the problem was before or after that. Could be a bad solder joint or a capacitor arcing through at higher voltage or something. Or a transistor breaking over at higher currents.
Then I would look at the input of the VAS transistor and see if the problem was before or after that. Could be a bad solder joint or a capacitor arcing through at higher voltage or something. Or a transistor breaking over at higher currents.
There is enough there to be useful. Even with half the page missing.
With a music input or sine wave input I'd look at input and output of Q12, the MJ340. That place is kind of the divider between inputs and outputs.
Usually PA & instrument amp repair people just start ripping off output transistors, then the drivers, but with that weird waveform only under high drive it could easily be something cheap. General trouble shooting theory says to chop the problem in half with one test, then look to the bad side of the divider point, (before or after) and chop that in half with another test. That is the fastest on any general system.
With a music input or sine wave input I'd look at input and output of Q12, the MJ340. That place is kind of the divider between inputs and outputs.
Usually PA & instrument amp repair people just start ripping off output transistors, then the drivers, but with that weird waveform only under high drive it could easily be something cheap. General trouble shooting theory says to chop the problem in half with one test, then look to the bad side of the divider point, (before or after) and chop that in half with another test. That is the fastest on any general system.
Hi Folks; just an update:
Thanks to a helpful member of another forum and the service department at Traynor/Yorkville Sound, I have received both a service manual and owner's manual. (Attached below).
Thanks for the help so far. While testing to see if load/no load had an effect, I noticed 135 mV DC offset on the bad (channel B) side. Offset dropped to 125 mV w/ load. The output a low level (3 or 4 volts) was clean. After several minutes, the DC offset disappeared, and the signal simultaneously became distorted. I repeated testing the amp, powering down for several minutes seems to temporarily reset things. At one point, the bad channel developed 33 VAC--even with a dummy load, before collapsing into oscillating spikes.
Both the owner and service manuals have very detailed test/trouble shooting instruction. I will now attempt to remove the functioning Chan A VAS/Driver/Output assembly, which is blocking access to Chan B, below. Hopefully, Chan B will remain functional and serviceable, with Chan A removed.
Thanks Jo, for the trouble shooting tips, don't think there is enough 'rope' to allow the modules to function out of the case, but there are numerous test points, with explanations in the manuals.
Thanks Craig, for the no-load suggestion; so far it seemed that no load allowed slightly higher output, before latching into oscillation/distortion.
Back with pics, soon! Peter
Thanks to a helpful member of another forum and the service department at Traynor/Yorkville Sound, I have received both a service manual and owner's manual. (Attached below).
Thanks for the help so far. While testing to see if load/no load had an effect, I noticed 135 mV DC offset on the bad (channel B) side. Offset dropped to 125 mV w/ load. The output a low level (3 or 4 volts) was clean. After several minutes, the DC offset disappeared, and the signal simultaneously became distorted. I repeated testing the amp, powering down for several minutes seems to temporarily reset things. At one point, the bad channel developed 33 VAC--even with a dummy load, before collapsing into oscillating spikes.
Both the owner and service manuals have very detailed test/trouble shooting instruction. I will now attempt to remove the functioning Chan A VAS/Driver/Output assembly, which is blocking access to Chan B, below. Hopefully, Chan B will remain functional and serviceable, with Chan A removed.
Thanks Jo, for the trouble shooting tips, don't think there is enough 'rope' to allow the modules to function out of the case, but there are numerous test points, with explanations in the manuals.
Thanks Craig, for the no-load suggestion; so far it seemed that no load allowed slightly higher output, before latching into oscillation/distortion.
Back with pics, soon! Peter
"Traynor" was the man and his amps, "Yorkville" was his company as far back as 1963. Yorkville History
Yorkville has been down and up since then and indeed we can't know what files they held onto.
Hi Peter . I am working on Beta 800. On the amplifier boards there are 2 red leds.
O the bottom B channel they are lit.
On the top A channel they are not on but the channel still works.
Are these leds suppose to be on or off.
Anyone else that has the answer could give me this information??
Thanks
Paul
O the bottom B channel they are lit.
On the top A channel they are not on but the channel still works.
Are these leds suppose to be on or off.
Anyone else that has the answer could give me this information??
Thanks
Paul
Sounds like it's time to dig my beta800 out and start poking around at it again. It had very similar problems when I put it away years ago. One time I did consider transistor replacement as it had been heavily abused over the years, but sourcing BF871 / 872 was problematic.
Periodically I poke around the internet searching for something newer to swap in, but keep getting distracted and moving it further down the priority list of projects.
Hopefully finding this thread is what I needed to get motivated again
Periodically I poke around the internet searching for something newer to swap in, but keep getting distracted and moving it further down the priority list of projects.
Hopefully finding this thread is what I needed to get motivated again
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