Recent content by wattsabundant

The data sheet tells it all. Who knows what it sounds like, but it does protect itself.

As one of my post retirement jobs, I'm doing repairs here and there for a local shop, Stereo Lab, In Columbus Ohio. Many years ago there were Japanese data manuals for semiconductors. One that is very beneficial for vintage gear is the Transistor Substitution Manual. The latest version I have...

Every time you replace the fuse you do at least $50 more damage. With both output modules removed, bring it up with a 60 watt bulb or so and a 5 amp fuse. If successful discharge the caps and install one module and bring it up on a 100 watt bulb. If the bulb doesn't dim then switch to the...

I have the drop-in relay board. Also have a few of the power switches. Highly recommend my triac power switching board to avoid switch failure.

Jump on it. URIE is high quality pro gear. If you don’t like it, I’ll buy it.

An oscilloscope is of use only if you have a decent oscillator. The HP 204 is cheap, plentiful, and relatively low distortion. Digital scopes have their advantages that can be good if you need to capture waveforms. I bought a Rigol 4 channel scope with all of the bells and whistles and sent...

A cheap load bank can be made with hot water tank heaters. Home depot has a 240 volt version that is very close to 8 ohms. Downside is they have to be submerged in water or they burn up immediately. A 5 gallon bucket with a metal lid works well.

The 4000 is a disaster waiting to happen. It was designed before double sided boards with plated holes were available. It has a mother board with male connector pins and daughter boards that plug in. The pins on the motherboard have cracked solder joints. If a 4000 is going to be used it...

Transistor failure modes are open and shorted. Any meter with a diode function will meet this requirement. This includes $10 versions at Harbor Freight. I've tested 1000's of diodes and transistors this way. More advanced devices have a display and list NPN or PNP, type of device and current...

Well, you've certainly been busy. A few thoughts: I'm not sure what the quality of the pots are, but it is a minor concern for reliability with them mounted directly to the board. Of course, plated through holes help. I think very few people will want to buy the equipment to work with surface...

Sometimes you do things, not because you have to, but because you can. As I'm now retired I can take the time to mark up the schematic with Joe's comments. See attached. I think I know opamp theory reasonably well, but the tone control schematic gives me a headache. Joe, can you explain...

I’ve got a pile of the original jacks for the 200. Bought them last year when a surplus place was closing up shop. If you want exact original replacements, let me know I just looked at the jacks I bought. Apparently, I didn’t understand their function. With nothing plugged in to the jack, the...

I didn't get very far and abandoned it.

I'm not sure that shorting type is such a god idea. The 2000 I tried was noisey and I wondered if the shorting current in the ground traces from the shorting jacks contributed to that.

Cabbage Cases is in my back yard, figuratively speaking. They're legendary since the early 70's in Central Ohio. You can do a one off like a P.L. 400 case, or a complete world tour, and you get the same treatment. Road gear that holds up to the abuse of baggage handlers and roadies who are...