Pyramid Audio

OMG, customer sent this in for warranty repair because the display is stuck on HDMI and the volume Control is stuck at 31. Yes, that is a sticker on the front.

I learned a new skill, winding coils. A rare Technics SP-10 MKII arrived at the shop, and it would only spin very very fast. I was able to measure that one of the two FG coils was open. So I bought a coil winder. I unwound the bad coil so I knew I needed at least 225' of wire. I measured the diameter of several strands. Bought 38 gauge enameled wire from RE*****ON 12oz 38GA is 2495 feet. Practice practice practice. Finally wound the coil for real. Reassembled and AND IT WORKS!!

I was working on an old Sony STR – 252. At replacing the bad STK463. I noticed that one channel had an over one percent distortion in one channel. lot of distortion, really weird looking distortion. Not clipping not noise. As I adjusted the bass control, but distortion would go up and down and at maximum boost the distortion about normal. I decided to shotgun, but looks like tantalum capacitors, and that solved the problem. Then I tried to measure the capacitors for a fault. Couldn’t do it, ESR was correct , value was correct, loss was correct.  I remember Hase procedure from Audi magazine decade to Dr. Leach did made a wire adapter. The distortion analyzer input and output was directly across the capacitor. 

Talk about a blast from the past. early 80s I actually owned one of these . Now I’m working on one.

I heard a semiconductor vendor closed, NTE. Earlier this year BND closed. Yesterday I had problems trying to find a suitable pair of output transistors. A1106/C2581 subs to A1491/C3855. finally sub to TTA001/TTC002. i'm running out. where do you get good semis?

finally got a updated web page for my Shop,

PYRAMID AUDIO — Audio & Video Repair Center Service Center for Home Audio and Home Theater Products

The signal diodes I chose for the STV-X have more forward drop than the SANKEN version. This was due to space constraints.

This is a great replacement.
But in cases where the current through the bias diode is over 6 mA the bias adjustment pot might not adjust to the correct value.

I have found a more suitable mix of parts to make a better duplicate of the Sanken original.

parts are on order.

I recently did a thermal tracking test from 0 to 80 Celsius comparing my part to the Sanken. Placed in a stirred mineral oil bath, the parts were in series so the current was the same. I tested at 1 and 3 mA. I was pleased to see the voltage drop difference tracked closely. But my part has an almost constant 0.500V higher drop. So changes coming.

Anyone who had problems with the first version can swap for the new one.

Stranded  at the Hampton Inn Indianapolis. after 16 Hour drive from Fort Worth the car started once this morning. I moved it a couple of spaces to load. The next time it cranked with not a hint of catching I’m waiting for Mobil mechanics to call me back. Might not be a very good vacation.

Long distance customer asked about the Sharp S-603 output IC use in the Optonica SM7100. Compare to my notes this is the Sanken S-60. Any other observations?