I picked up a Phase Linear Series II Model 200 off of eBay for $40. It needs work.
It blew fuses, and the genius that owned it before me bridged the fuses with a wire. One of the outputs on the left channel was bad, and bridging the fuses caused all of the balance resistors in the left channel to fry. Also blew a couple of diodes here and there.
Got the left channel all back together and sorted. Waiting on some resistors to finish the job. In the meantime, I started tackling the right channel. All of the output transistors tested good, so that was nice. BUT, with the outputs removed I'm getting 65v DC output to the speakers. (Which means the speaker relay never engages, it stays in protection mode).
I'm not an electronics guru. I have a meter, but no scope and no test equipment. I'm just guessing that one of the driver transistors is shorted, but I have no idea how to determine which one, or if that's even the problem.
Fortunately this is a very simple amp, very simple design. The service manual, including schematic and parts layout, is located here:
AK Database PDF Gallery - Phase Linear/Phase Linear 200 Series Two Service Manual
Any advice on how 65 volts DC (rail voltage) is making its way to the speakers with the output transistors removed would be appreciated.
Thanks!
Charles.
It blew fuses, and the genius that owned it before me bridged the fuses with a wire. One of the outputs on the left channel was bad, and bridging the fuses caused all of the balance resistors in the left channel to fry. Also blew a couple of diodes here and there.
Got the left channel all back together and sorted. Waiting on some resistors to finish the job. In the meantime, I started tackling the right channel. All of the output transistors tested good, so that was nice. BUT, with the outputs removed I'm getting 65v DC output to the speakers. (Which means the speaker relay never engages, it stays in protection mode).
I'm not an electronics guru. I have a meter, but no scope and no test equipment. I'm just guessing that one of the driver transistors is shorted, but I have no idea how to determine which one, or if that's even the problem.
Fortunately this is a very simple amp, very simple design. The service manual, including schematic and parts layout, is located here:
AK Database PDF Gallery - Phase Linear/Phase Linear 200 Series Two Service Manual
Any advice on how 65 volts DC (rail voltage) is making its way to the speakers with the output transistors removed would be appreciated.
Thanks!
Charles.
The usual diode test may work. The B-E should be a diode, as should the B-C.
For NPN types, the positive meter lead goes to the base.
They seldom will measure ok this way and still have a C-E short, but it's remotely possible.
A transistor tester is useful.
Some multimeters have them.
I bought an Atlas Peak semiconductor tester.
You can connect the transistor any way and it detects what it is.
It tells you the gain of the transistor too which is useful.
I once had a fault where the transistor buzzed out ok but only had a gain of 1 !
Some multimeters have them.
I bought an Atlas Peak semiconductor tester.
You can connect the transistor any way and it detects what it is.
It tells you the gain of the transistor too which is useful.
I once had a fault where the transistor buzzed out ok but only had a gain of 1 !
Hhere's what I've got so far:
Left channel removed completely.
Right channel installed, but output transistors NOT installed.
Relay never trips, and there's 65 volts on the right channel speaker output. (thank you little relay)
If I remove BOTH drivers (Q4 and Q9), and then power up, the relay DOES trip, and there's 0 volts on the speaker output. If one or the other are installed, the relay will not trip, and there's 17-20 volts or so on the output line. But I've tested both transistors, and the emitter and collector are NOT shorted.
I haven't removed Q2 or Q3, but there aren't any dead shorts between emitter or collector on them either.
I've checked for blobs of solder, broken traces, and the like. I've replaced a couple of diodes that looked a little charred, but they actually tested fine. All four output transistors also tested fine, even though they're not currently installed in the circuit.
Any idea what could be causing this? I'm a computer scientist, circuits are not my thing. My knowledge here is rudimentary. I'd appreciate any help you can give.
Charles.
Left channel removed completely.
Right channel installed, but output transistors NOT installed.
Relay never trips, and there's 65 volts on the right channel speaker output. (thank you little relay)
If I remove BOTH drivers (Q4 and Q9), and then power up, the relay DOES trip, and there's 0 volts on the speaker output. If one or the other are installed, the relay will not trip, and there's 17-20 volts or so on the output line. But I've tested both transistors, and the emitter and collector are NOT shorted.
I haven't removed Q2 or Q3, but there aren't any dead shorts between emitter or collector on them either.
I've checked for blobs of solder, broken traces, and the like. I've replaced a couple of diodes that looked a little charred, but they actually tested fine. All four output transistors also tested fine, even though they're not currently installed in the circuit.
Any idea what could be causing this? I'm a computer scientist, circuits are not my thing. My knowledge here is rudimentary. I'd appreciate any help you can give.
Charles.
I need some help. I've replaced all of the transistors in my Series II Model 200. I've verified that they're all installed correctly. I've replaced the two zener diodes and the two black diodes. I've replaced any of the little diodes that tested bad. I've replaced the four balance resistors. I installed only one channel, (leaving the black and red wires for the other channel unconnected) and I'm getting 65VDC on the output wire (gray wire, tested against chassis ground). This happens with or without the output transistors installed (all four test good). I've verified that there are no solder bridges or broken traces on the board. I'm at a complete loss as to what the problem could be.
This is the same problem I purchased the transistor kit to fix, and it didn't fix it. Do you guys have any idea what could be causing this? I could really use your help. Thanks.
Charles.
This is the same problem I purchased the transistor kit to fix, and it didn't fix it. Do you guys have any idea what could be causing this? I could really use your help. Thanks.
Charles.
There are only two electrolytics. I replaced C2 (100uf) because I had a couple of replacements lying around. C6 (47uf 100v) is the other electrolytic, and I don't have a replacement on hand right now. I will go back through and test all of the resistors and capacitors. I hope I didn't fry my new parts... *so* frustrated.
Charles.
Charles.
Its always worth powering up using a mains lamp in series with the mains if you aren't sure. It will limit the current.
On my new amps I usually power up without a mains lamp but don't connect a speaker and I monitor the output on a scope to see if I am getting a rail voltage on the output.
Only then would I consider connecting a speaker.
If you didn't have a speaker connected then its possible you got away with it.
The problems arise if both phases of output transistor turn on at the same time.
On my new amps I usually power up without a mains lamp but don't connect a speaker and I monitor the output on a scope to see if I am getting a rail voltage on the output.
Only then would I consider connecting a speaker.
If you didn't have a speaker connected then its possible you got away with it.
The problems arise if both phases of output transistor turn on at the same time.
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Charles
I rebuilt the 200 Series II a few years ago. I remember I replaced all the transistors with newer numbers because the original ones were long discontinued. I'm quite certain I changed the outputs to MJ15024 and MJ15025. There are some minor mods that I did as well to improve the performance. If you like, I can try to dig up my files.
Regards
Mike
AmpsLab
I rebuilt the 200 Series II a few years ago. I remember I replaced all the transistors with newer numbers because the original ones were long discontinued. I'm quite certain I changed the outputs to MJ15024 and MJ15025. There are some minor mods that I did as well to improve the performance. If you like, I can try to dig up my files.
Regards
Mike
AmpsLab
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