So, here I go. Phase Linear 400

[VSAT88]

Collector to emitter test with ground of the meter on the collector buss bar.
All readings at 200 Ohm scale

Row 1.
006
006
001

Row 2.
009
009
005

Row 3.
No reading on 200 Ohm scale

Row 4.
No reading on 200 Ohm scale



Base to emitter test with ground of the meter on the base buss bar.
All readings at 200 Ohm scale.

Row 1.
008
008
002

Row 2.
1.5
1.6
1.2

Row 3.
12.9
13.6
13.6

Row 4.
12.2
12.1
12.2
12.2

 

[VSAT88]

By the way. The service manual states "Read across R36 and R37. A reading less than 150 ohms indicated a defective output driver" . I did the test across both but I do not understand how you could get any less of a reading than 150 ohms as the resistor at R36 and R37 are both 150 ohm...

 

[laatsch55]

A shorted driver will have less resistance across the semiconductor junction than the resistor....

 

[laatsch55]

Base to emitter should be at least 10 ohms, due to the 10 ohm bias resistor.

 

[laatsch55]

To be sure of the outputs, pull all and do a diode check of the base/emitter, base/collector jct's....

 

[VSAT88]

I thought that would be a good idea myself. With readings like that I am confused. In fact I have been confused for a while on this one. I am disappointing with myself on this one. I tried the best I could but sometimes things happen. I do thank you and I will report back in soon.

 

[laatsch55]

We'll get through it bud...

 

[Billboard]

VSAT88, you are doing great, Lee will get you through this, if you do exactly as he says and no more you will get your amp fixed, and you are following along perfectly. The amp will be singing soon, don't get discouraged.

I have seen many threads were Lee magically and remotely gets amps working (mine included), and I have seen a few never fire up because some people just cannot listen to instructions.

 

[VSAT88]

Thanks for the vote of confidence. I will do exactly as he says and...no more !

 

[Skratch]

Thanks for the vote of confidence. I will do exactly as he says and...no more !

Once you figure them out its a piece of cake, they are pretty straight forward amps

 

[laatsch55]

Dayam!!! The skratchman posts!!!!!

 

[laatsch55]

Let's not forget Joe, Jer, and the rest of the folks around here, they have pulled my as out of the fire many times.

 

[Skratch]

Dayam!!! The skratchman posts!!!!!

Been laying low, pretty much playing with vinyl and reel to reels

 

[Fishoz]

Hey Skratch...Elkhorn WI flea this weekend. I'm going Saturday. If you're headed up there let me know. Last one of the season - last month tons of shit but $$$$, they got to get rid of shit this time.

 

[VSAT88]

Checking in. Just wanted to thank you guys again for your support. I have not been able to get back out to the shop to pull the OPT yet but I have not forgotten my mission. Hope to get back in the swing of things soon.

 

[laatsch55]

Coolness....

 

[Bradrock]

The suspense is killing me! I need a fix! Have to go read some more old threads.

 

[VSAT88]

Back again. tested first three OPT all test good, no opens no shorts. Should I put them back in when I am done or leave them all out ?

 

[VSAT88]

Found two bad ones both on the right channel. viewed from behind the amp with the transformer on the right. Row three third output tx down from the top is bad. Row 4 is the same, The third output tx is bad. The two suspects were found on row 4 the first and second one down. I have all the output tx pulled out and I will await farther instruction before doing anything else. The drivers are still in place.

 

[laatsch55]

Pull the drivers too and check them.....then read this....

http://forums.phxaudiotape.com/show...-latch-up-tendency-in-Phase-Linear-Amplifiers