Re: 2230 PSU Replacement Component Choices


alastair.knights@...
 

I thought I ought to answer my original question in case it helps others. Back in March 2021, I asked for advice about suitable replacement parts for a 2230 PSU and based on tests, the answers seem to be:

Q935, ‘Thyristor, SCR 8A, 200V sens gate - I tried using a ST Micro TS820-600T as a replacement, but it triggered unexpectedly and burn out, so this device may be too sensitive. So, I kept the old GE C10682 part in service.

Q946 and Q947, ‘Transistor NPN, 50V, 150mA, 200mW, inverter’ - I tried using On Semi MJE15032G as replacements, but the inverter would not oscillate reliably or continuously. It seems likely that hFE and possibly capacitance are major factors in whether the inverter oscillates. My MJE15032Gs have an hFE=96 while the original transistors are only hFE=48. Once again the original transistors were retained.

Q9070, ‘MOSFET, N-channel, TO-220’ - I used a Toshiba TK10E60W as a replacement and this worked fine. I also bolted a small finned heatsink onto the back of the main mounting plate using the Q9070 fixing screw and this lowered the temperature of the mounting plate by around 10 degrees C (max temp was 46C after 30mins).

(VR935, ‘Zener, 51V, 5%’, SZG35009K7 (1N978B), There was no need to replace this as it only needs replacing to make room for the revised SCR location described in Tek Product Modification 060-2239-03.)

CR907 (and CR906) - I used a MUR460 as a replacement but the leads are too large to fit in the holes on the PCB. However, binding the thick MUR460 leads onto the stumps of the old diode is a simple fix (please don't drill out the THP hole!)

Apart from the RIFA caps in the Line Input Filter, the only other component that I felt needed replacing was C907, which has to pass very high ripple currents of many amps. Despite the original being a high-quality TRW film capacitor, given its 35 years of service and critical location, I replaced it with a 630V Panasonic ECQE6105JF cap.

Hope this helps someone as previous postings have helped me.

Alastair Knights

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