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Old 11th December 2008, 03:05 AM   #1
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Default Diode Question

I've decided to repair/revamp a guitar amplifier kit that I originally put together in 1974. It was offered by the now out-of-business Southwest Technical Products Corporation out of San Antonio Texas.

The power amplifier uses a couple of transistors, NTE180 and NTE181, attached to a heat sink with two diodes, NTE5801, thermally coupled to the transistors by diode clamps.

The instructions specifically say "diodes D1 and D2 are thermally coupled to Q4 and Q5 by means of a heat sink and diode clamps".

The best that I can tell, the clamps appear to be a band of metal going around the diodes and being secured to the heat sink by the bolts/nuts securing the transistors.

I can't seem to find anything about diode clamps on the internet to buy some. Any help or information would be appreciated.

I didn't do this right the first time around and something failed after a period of time and I suspect something in the power amplifier circuit.
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Old 11th December 2008, 03:53 AM   #2
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Location: Canandaigua, NY USA
I haven't seen the circuit, but SWTP used a small metal radial lead diode in many of their designs (Tiger for one). It worked well, and I just make my own clamps out of a piece of brass or aluminum shim stock. You could even use a piece of roofing flashing- just cut a strip with scissors and bend it around the diode. It certainly isn't anything one would bother buying. BTW, I have a lot of those diodes- if you need any, just pm me.
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Old 11th December 2008, 01:47 PM   #3
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Wow! Thanks for the quick response. I was thinking of fashioning some out of thin metal if it came to it.

If I can't find any diodes, I'll let you know. I was having trouble finding some of the old parts until I found a good part number cross reference.
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Old 14th December 2008, 10:00 PM   #4
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Iíve got a couple of questions. I did a search on this forum for SWTPC; got a few hits on the Tiger posts, and read them. Some of the advice seems to apply to the MMM Amplifier, so I had a few questions. I donít think the power amp and preamp sections between the Tiger and MMM are exactly the same, but many of the same transistors are used.

Itís mentioned in these posts for the Tiger to either replace the MJ802/4502 with the MJ15003, MJ4281, MJW21196, or 2N3773 which for which. It is also mentioned as an alternative to double up on the output devices; Iím assuming this means to parallel two of the MJ802s with each other and two of the MJ4502s with each other?

Power supply and power amp capacitor (in series with speaker) Ė Iím assuming itís ok to go a little above on the capacitor voltage rating due to availability?
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Old 14th December 2008, 10:40 PM   #5
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Links to schematics of the power supply and power amp:

http://i23.photobucket.com/albums/b3...hen/mmm-pa.jpg

http://i23.photobucket.com/albums/b3...hen/mmm-ps.jpg
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