Ready to shoot my Series 2 Model 200

C

ChopperCharles

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I bought it for $40, blowing fuses. I thought it'd be an easy fix -- replace the bad power transistors and go.
Unfortunately, that's not the case. I kept blowing B+ fuses on initial power up, even with the output transistors removed.

Pulled ALL of the output transistors, pulled both channels, and replaced every single transistor on both boards with parts from a kit off of eBay. Most of the diodes too.

I attached one channel, no output transistors installed, and powered it up. R12 fried immediately.

I can't even get it working to the point where I can test voltages to try and see what is wrong.

I'm beyond frustrated with this thing, and I'm ready to use it for target practice.

Charles.
 
laatsch55

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Did you check transformer secondary voltages? Did you check DC at the bridge rectifier?
 
ksrigg

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There are some brilliant Phase Linear experts on this forum, and I know they could repair a 400 while sleeping, but it will cost some serious money, and will take time. If you want to repair it yourself, there are many posts to show you the way. There are also several really nice guys who may restore your amp for you. It is not cheap, but when you get the amp rebuilt you will have a state of the art amp that will kill anything else on the planet.
 
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ChopperCharles

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Mauser 7.92x57

I don't know what a bridge rectifier is or looks like.

With no channels installed, I get +70v on the red wire and -70v on the black wire.
With one channel installed, which has all tested good output transistors, when I power up the B+ fuse immediately blows
If I remove the output transistors from that channel, replace the fuse, and power it up, R12 fries. So the problem is not the outputs.

I've replaced all of the transistors and most of the diodes with new parts from the ebay seller qua-co. He had a kit designed specifically for the 200 series II.

The service manual is here: http://akdatabase.org/AKview/albums/userpics/10007/Phase Linear 200 Series Two Service Manual.pdf

The amp circuit is simple-seeming, but I can't follow how it works. I'm a software engineer, hardware is not my thing. Transistors are magic to me.

I did post on Audiokarma, but they couldn't help and said to come here. This is my last-ditch attempt at fixing it.

Charles.
 
MarkWComer

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ChopperCharles said:
Mauser 7.92x57

I don't know what a bridge rectifier is or looks like.
Click to expand...
It's a square thing about 1 1/8" on a side, maybe about a half inch tall. Has four pins sticking out, one pin rotated 90° from the other three. The rotated pin is the positive terminal, the pin that's diagonally opposite is the negative terminal. The other two pins are AC, neither negative or positive.

This is the device that converts AC to DC.

Yes- transistors are magical things! Not only do they have electron flow (movement of free electrons), but they have hole flow (movement of electron deficits). Amazing!
 
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30Weight

30Weight

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I just finished the repair on one awhile back.Same problems as yours.I didn't use the qua-co kit,although I have done business with him before and am a happy customer. Fellow on ebay,Lou Dorens (?) LDX Technologies (?) has repair and upgrade kits for it.He put together the repair kit after I consulted him regarding the issues with mine. I used both,quite happy with how it turned out.I ordered the kits years ago,and like you got frustrated with the repair so it sat for quite awhile.The big problem with it was that 1 of the power supply caps was bad,blew everything out.The caps,Cornell-Dubellier,are available at Mouser under the same part number that was printed on the original C-D caps.About $15 each if I recall.I also replaced the bridge rectifier even tho the original tested good. I was unsure of its continued reliability. If I recall I ordered it from Newark,possibly using the part number from the original. It's currently at my friends vintage audio shop,for sale.I have the documentation package with the amp,that's why I'm a little hazy on the details.When I make it into town next I'll stop by and get the details. That's a sweet sounding little amp.........
 
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ChopperCharles

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Well, since I'm getting 70v and -70v out when the powering the unit with no channel boards installed, I think the power supply and bridge rectifier are fine. Bridge rectifier is apparently bolted to the chassis, and hidden by the caps, that's why I missed it.

Yes, this is the amp I need to the 2sd555's for.

I replaced C2 because I had them. I didn't replace C6 because I didn't have any of that voltage and value. Those are the only two electrolytics, and neither were (or are) shorted.

Charles.
 
Gepetto

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ChopperCharles said:
I bought it for $40, blowing fuses. I thought it'd be an easy fix -- replace the bad power transistors and go.
Unfortunately, that's not the case. I kept blowing B+ fuses on initial power up, even with the output transistors removed.

Pulled ALL of the output transistors, pulled both channels, and replaced every single transistor on both boards with parts from a kit off of eBay. Most of the diodes too.

I attached one channel, no output transistors installed, and powered it up. R12 fried immediately.

I can't even get it working to the point where I can test voltages to try and see what is wrong.

I'm beyond frustrated with this thing, and I'm ready to use it for target practice.

Charles.
Click to expand...
It is usually the TO-220 predrivers on each of the amp boards that are shot. I have brought a couple of these back to life a long while ago. Both were that problem along with a bunch of lifted trace from prior owner repair attempts.
 
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ChopperCharles

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I replaced the pre-drivers. I'm still frying R12 and R17, even with no outputs transistors installed. Pre-drivers are not shorted in any way.


Charles.
 
Gepetto

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ChopperCharles said:
I replaced the pre-drivers. I'm still frying R12 and R17, even with no outputs transistors installed. Pre-drivers are not shorted in any way.


Charles.
Click to expand...
Then your bias clamp in the Q2 position is not working properly. You are probably taking out fuses too...
 
wattsabundant

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I'm assuming this is only happening on one channel. Unfortunately when you replaced everything on the board you may have induced more problems. that is not usually a vey effective troubleshooting method. I would suggest:

  1. Download the service manual and read it cover to cover. It has an exceellent troubleshooting section. I posted it on digital docs at Audio Karma
  2. Compare the good channel to the bad channel for proper parts installation.
  3. Build the dimbulb tester and use it.with a 40 watt bulb to start
  4. Disconnect the bad channel from the power supply
  5. Verify the power supply is ok. Verify that both large caps have the san DC voltage on the
  6. read the manual about testing the power transistors acheck all of them Check to makesure none are shorted.
  7. Do what the manual says
  8. use a jumper wire between the bases of q4 and q9 to keep q9 and q4 from turning on
  9. If that fails send it to me and I'll fixit.
 
Gepetto

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ChopperCharles said:
I replaced the pre-drivers. I'm still frying R12 and R17, even with no outputs transistors installed. Pre-drivers are not shorted in any way.


Charles.
Click to expand...
In your AK post, you said you replaced all the transistors.

What did you replace them with?

Please identify the transistors:

Q5, Q6 = ??
Q10, Q11 = ??
Q4 = ??
Q9 =??
Q3 = ??
Q1 = ??
Q2 = ??
Q7 = ??
Q8 = ??

What device is in the Z1 location? Did you replace that too?
 
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