If you have a DMM with a diode range you can use that to test them if the meter puts out high enough voltage. If you have a second meter you can measure the voltage on the diode testing meter leads. If it's 2V or more you can test STVs with it.
It sounds like the current limiting resistor in the meter is dropping too much voltage. You will have to go with plan b. Use a bench power supply or a 9V battery and a 1K resistor in series with it, and connect it to the STV out of circuit. Then measure the voltage drop across the STV.My Fluke 77II put out 7.3V, can I test the STVs directly using this meter. I'm asking because I have a bad STV-4H, and I was looking at my stash of STVs, All STV-3hs and was measuring them, and getting approx 1.9v across them, I was thinking of just adding a diode in series with it and calling it good. I then remembered a QX-949 parts unit that I have and pulled the two STV-4hs out of it and they measured the same, 1.9v. I thought I would read approx 2.4 volts across the 4-Hs.
The transistor bias control works very well. That's what most amps use. You put the bias pot in the bottom of the voltage divider on the base of the bias transistor, so if it opens, the bias transistor goes into full conduction and turns off the bias. (Some designers didn't think of that and put the pot in the top of the divider, so when the pot opens the transistor shuts off and the amp gets full bias and blows the outputs.)
I tested that a while back, I took a pair of #24 bare copper wires, and made 2 parallel lines 1/16 of an inch apart, then dribbled a jbweld puddle onto them and let it harden.
Then after it hardened, I tested resistance, and leakage current with up to 30 volts across the wires. Nada. down to the microamps.
I tested it because, when the leads break off flush with the stv-xh body, I dig down to good wire (~1/32"), solder on flexible leads and jbweld it all together.
Send me your busted diodes, and I'll try the same for you, I'm actually getting good at it, and have made a mold.
I've taken some measurements of SV03 variants and SV04. They seem to measure quite different to the STV-03H and STV-04H. Maybe relevant to folks stumbling onto this thread. A work in progress for suitable sub... results being posted over in am Sansui AU-X11 thread.
Bumping this thread - in replacing a DC offset pot in my Pioneer M22, of course I broke the leads on probably the worst component to do this on - the STV-4H. Reading Hyperions' original post here - is four UF1004's in series still a good replacement? Their dimensions seem to be OK to fit into the amplifier's heatsink recess.
ARGH. Thanks
If Glenn is unable to help, I have a couple STV-4H's and will make one available.I've found that four UF1004's track the temperature pretty well. But on something like the Pioneer running in Class A, I'd try real hard to locate a real STV-4H diode.
I'm working a deal now with a seller who has a few of them. If it goes through, we'll see about getting you one.
Thanks you very much Mark, I busted one wire off of my daughters 2220b last night while recapping. I had already started exposing the stubbed wire with my dremel when I ran across this thread. I must say, it was nice to know that somebody had successfully tried it before and was able to walk me through the procedure. Holding my breath and crossing my fingers that it will work tomorrow when I reassemble the amp board.I tested that a while back, I took a pair of #24 bare copper wires, and made 2 parallel lines 1/16 of an inch apart, then dribbled a jbweld puddle onto them and let it harden.
Then after it hardened, I tested resistance, and leakage current with up to 30 volts across the wires. Nada. down to the microamps.
I tested it because, when the leads break off flush with the stv-xh body, I dig down to good wire (~1/32"), solder on flexible leads and jbweld it all together.
Send me your busted diodes, and I'll try the same for you, I'm actually getting good at it, and have made a mold.
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