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An ultra reliable 400 would use the 700 chassis and heatsinks with the bolt pattern of a 400 transformer. 10 outputs per channel = lower dissipation by each one. It would be hard to blow that one.

Not to argue, but my experience was there were racks and racks of 400's in rocke and roll PA's. They wered modified with front panel fuses and level controls. When done right, the lower outside transformer bolt was replaced with a longer one and a bracket was installed to support the...

As for the noise, the input jacks "float" from the chassis. Float means they are not directly connected to the chassis. The jacks should have a fiber washer on both sides of the chassis. Sometimes people eliminate the washers thinking it will improve noise. I think not.

Looks like my brother's writing. He's an architect.

There was a commercial a few years ago with a vintage Marantz receiver but they Photoshopped Marantz off of the front panel.

for the time being send me a PM if there is a dire need.

I enjoy identifying vintage audio gear in movies and TV shows. I've watched all of the Bosch seasons on Amazon. Every once in a while there is a shot of his home music system. The system appears to be a McIntosh 240 amp and a McIntosh preamp, Marantz turntable, and Ohm Walsh speakers. Season...

Hi Mark. Joe recently mentioned you are building boards for him. I get mine built by the lady who runs the PCB test dept at my day job. She's got all of the quals and does a great job. It just takes a while. Perry did a run for me a few years ago. He does good work. Are you interested?

I still have an unpublished Earthlink account with a couple domains. Earthlink still offers dial up. Been working on a new web site forever. When it's done the current Watts Abundant content will be replaced. All of my original P/L service manuals (50+) are uploaded. Also have early...

Summary?

The original nut that comes with the binding posts from the OEM are indeed 4-40 x 3/16. On 400's I supply a 4-40 x1/4" keps nut (attached external tooth lockwasher). For 700's, the board mounts to standoffs that screw on to the binding post. I supply a 4-40 screw with attached external...

I've got a 700B with what looks like #10 solid copper and solder lugs for the ground bus. The photo I posted was sent to me and the wiring looks like a factory job. Doesn't matter as it will go away.

Anybody seen this? I don't think I've seen this bus wire for the ground nor the soldered connections on the caps.

Be careful handling them as the leads can break. If a lead breaks off you blow the channel.

When using mica, which I don't, a drop of grease the diameter of a number 2 pencil, between the pins is all that is needed. Have to use it on both sides. Less is more. I've never had a silpad fail. Of course I never reuse one either.

I did a post a year or so ago about a temperature controller for tower computers. The controller has thermocouples that read heatsink temperatures and adjusts the speed of 12 VDC fan motors. After I got the thing assembled and tested I found that my amps (in walnut cabinets) did not heat up...

Listing is in Lancaster, PA. Is that still Clair Bro's home base?

The quasi comp versions has a parallel path that likes to oscillate if the RCA 410's are not used in the negative column. I found out the hard way. Credit to Joe on that one. Roll, when you replace the board, send me the old one. I'll do a failure analysis and try to determine if a board...

With all due respect to Mark, I don't like the latch up theory. I've personally never seen it. That doesn't mean it can't happen, I just haven't seen it. I have seen marginal front end transistors that would ocassionally result in full DC on the output at start up. Sometimes the amp would...

It's entirely possible that the front end transistors (Q1-4) are intermittent. That could cause DC offset that cascades to outputs. There are lots of other age related possibilities.