![]() I removed the two existing regulators and their adjustment resistors, and replaced all the filter capacitors on the power supply board. So, I'll replace the positive regulator with an LM317, and the negative regulator with an LM337, both of which should be available for the foreseeable future. Exact matching parts, in the odd package, are available from Europe for slightly less, but the shipping is $25 for each part! Considering I only paid $75 for the whole analyzer, there's no flipping way I'm putting that much into it for two little parts. *IF* you can find them, they go for $20~$30 each, plus shipping. These are obsolete parts, and on top of that, they're in an oddball package. The circuit uses a uA78MG for the positive side, and a uA79MG for the negative side. The (nominal) 24 Volt supply measured 27 VDC, while the (nominal) -24 Volt supply measured -30 VDC.įurther checking and experimenting revealed the negative supply regulator was toast, and regardless of what resistor values I used on the "Adjust" pin, the output stayed stuck at -30 VDC. ![]() The first few steps went fine, and then Murphy popped up again.
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