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Old 13th October 2012, 08:50 PM   #541
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O dear, Carl !

As I wrote on page 35 of my "Builder's Manual": move a MICA washer or silicone thermal conductive foil between the transistors' backs and the ALU-L profile.
Insulate the srews by means of "shoulder washers (? - see attached image) or polyamide screws and verify after soldering that all of the legs of all transistors
have infinite resistance to the ALU profile.

I hope that the BD139 was the only part that you fried.

I wish you good luck - Rudi_Ratlos
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File Type: png shoulder washers.PNG (34.0 KB, 389 views)
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Old 13th October 2012, 09:02 PM   #542
cjkpkg is offline cjkpkg  United States
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Well looks like the bd139 regulates the gates of the output transistors so I am thinking the bad channel fried it to short circuit and feed the output transistors full voltage.

I suppose I could swap the bd139 from the other side and validate my thinking.
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Old 13th October 2012, 09:45 PM   #543
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Carl, before you risk the remaining BD139:

Measure the resistance between all transistors' legs and the ALU-profile! Your DMM should read: infinite resistance!

Do not insert fuses into the on-board fuse-holders, but bypass them by a small 0.25W / 10 Ohm resistor!
This is the recommended procedure (documented in the builder's manual)!
An error like you did would have blown the 10Ohm resistor and not any precious transistor!

And please: use a bulb-tester as well!

Best regards - Rudi
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Old 14th October 2012, 04:07 PM   #544
cjkpkg is offline cjkpkg  United States
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I used my DMM in diode test mode on all transistors on board. The bad board reads EXACTLY the same as the good board...

This is most frustrating

All caps are correct.

There are no apparent shorts

Transistors all read the same via the quick transistor test.

I dont know what to do...

both rails still get 800+ mV upon startup immediately. Something is letting all that voltage through...I am still suspect of a bad BD139 since it is common to both rails...it must be something like that that is common.
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Old 14th October 2012, 04:34 PM   #545
cjkpkg is offline cjkpkg  United States
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Oh, and as a further slap in the face, the speaker protect boards are not functioning. The relays are not engaging.

Good grief.
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Old 15th October 2012, 03:36 PM   #546
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Carl, can I help you in any way?
If the relay on the speaker protection PCB is not engaging: one possible reason is that there is >1V DC on the speaker's output (I assume, this is the reason why).

I finished the SYMASYM for my brother yesterday night.
It is playing beautifully.

Best regards - Rudi_Ratlos
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File Type: jpg SYMASYM 018.jpg (223.4 KB, 356 views)
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Old 15th October 2012, 10:58 PM   #547
cjkpkg is offline cjkpkg  United States
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OK so I ordered a few replacement bits from mouser...I will attempt to get the other channel running this weekend.

One question...on the speaker protect is it really one leg of the A/C to the upper pin and a ground to the lower pin? I am not following that logic. I hooked up A/C to both pins an fear if that is not correct then I might have fried one or more of the ic's.

If you look at the connection diagram in the manual both legs come from the ground of the psu board.

Last edited by cjkpkg; 15th October 2012 at 11:07 PM.
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Old 16th October 2012, 06:11 AM   #548
tom6 is offline tom6  Australia
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Default vs FC-100?

Hello Rudi

Been following your threads on the TO-3 Symasym and also the FC-100. Now you've built the TO-3, I'm interested to know - which amp do you prefer or do they both have different strengths?

Thanks

Quote:
Originally Posted by Rudi_Ratlos View Post
Carl, can I help you in any way?
If the relay on the speaker protection PCB is not engaging: one possible reason is that there is >1V DC on the speaker's output (I assume, this is the reason why).

I finished the SYMASYM for my brother yesterday night.
It is playing beautifully.

Best regards - Rudi_Ratlos
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Old 18th October 2012, 06:35 PM   #549
scalpel is offline scalpel  United Kingdom
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Hello Rudi,I am joining the queue to say thank you for the outstanding boards and the selfless work you are doing helping us build these amps.My best regards,Manuel
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Old 19th October 2012, 04:50 PM   #550
joshvi is offline joshvi  India
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Hai Rudi,

I got the PCBs today.

thanks

best regards
joshvi
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