Got the transistors, installed them and the zeners.
The short is gone, amp powers up again and amplifys a signal.
I checked the power supplies again and everything is good +-39VDC and +-15.3VDC.
Ran the output thru the test equipment and the left channel THD is still high. The new transistors seem to be the real deal so far.
From the SA, there is still a lot of harmonics (even and odd) thru out the spectrum on the left channel.
The short is gone, amp powers up again and amplifys a signal.
I checked the power supplies again and everything is good +-39VDC and +-15.3VDC.
Ran the output thru the test equipment and the left channel THD is still high. The new transistors seem to be the real deal so far.
From the SA, there is still a lot of harmonics (even and odd) thru out the spectrum on the left channel.
This amp is driving me to drink
The ran for a while and then the left channel had +30V DC on the speaker terms.
Q109 was shorted again.
Replaced Q109 again, still had the DC offset. Looked for more bad transistors.
Found Q108 shorted B-E, 2SC3421
Replaced Q108
Powered it back up, no DC offset! But the Protect light was on and the L channel light was off.
Went thru the protect light circuit and found Q113 shorted.
Replaced Q113
When powered on the Protect light is off and the L channel light is on.
When I apply a signal to the input, the Protect light comes on and the L channel light goes off.
I think the bias circuit has a problem, that's where I'm headed next.
This is some real serious self inflicted pain!
I hope in all this I have replaced the noisy part that started all this!
The ran for a while and then the left channel had +30V DC on the speaker terms.
Q109 was shorted again.
Replaced Q109 again, still had the DC offset. Looked for more bad transistors.
Found Q108 shorted B-E, 2SC3421
Replaced Q108
Powered it back up, no DC offset! But the Protect light was on and the L channel light was off.
Went thru the protect light circuit and found Q113 shorted.
Replaced Q113
When powered on the Protect light is off and the L channel light is on.
When I apply a signal to the input, the Protect light comes on and the L channel light goes off.
I think the bias circuit has a problem, that's where I'm headed next.
This is some real serious self inflicted pain!
I hope in all this I have replaced the noisy part that started all this!
I'm about to pick up a V1, today that has been in regular service. In fact the owner has been using the speaker taps to power his headphones because he preference way it sounds to the headphone output. I'm curious why information about the headphone output stage on any version of this amp is so obscure. Yes, the manual says it can run as low as 8-Ohm headphones, but that doesn't tell me much. I'm hoping this amp will be a step up from my class-D Schiit Magni 3. I like it because it has copious amounts of power, and can power most anything with sufficient wattage, but it's still a budget amp. Sounds great with a good DAC, though.
Oh well, fingers crossed!
Oh well, fingers crossed!
With 30V DC on the output the input to U101B would have exceeded it's maximum voltage.
It would be worth checking.
Good luck
Sid
Hooked up the Zamp and had massive hum in both channels. Probably a ground loop as everything is running off the same power-strip. Maybe because I'm using a USB Audio Interface as a DAC and the ground loop is passing through my PC. I may try busting out the Schiit Modi 2 Uber I used to use and see if that helps.
A schematic for the V1 would definitely be handy for anyone who finds they are missing components or have damaged ones. I'm going to replace all the capacitors in mine because the capacitor tied to the trigger circuit for power-on happens to be the one that has blown. However, TEAPO capacitors are used throughout, and they are garbage caps, which are known to fail without visible signs so I'll make a record of all the diameters, lead spacing and of course voltage and capacitance values in case anyone else wants to throw the BOM into Digi-Key's ordering system and make their V1 function properly. It's a bit sad that Parasound took the time to build a toroidal supplied AB amp, but chintzed out on the components. I don't have it in front of me, right now but I'm sure there will be a few other components I'd like to replace while it's apart. Stay tuned!