1280 recap info

[Poasttoastie]

Cleaning up the Heat sinks to apply new thermal grease and noticed this on 3 out of the 4 output transistors. They still test as good. But, what could have caused this and should I replace them? For peace of mind I probably will if I can find some new. The 15-K capacitors all tested good with no leakage any of them. No visible other burned parts or popped caps on either boards or on the Power supply board or Protection circuit board.

 

[Craftsman11]

Hello:
I’ve been scouring threads to identify proper replacement diodes for the sx-1280 protection board with no luck. Can anyone suggest suitable replacements for D1,D2, and D3 on the awm-123? Does the 1n4148 work for d1 and d2? What about the replacement for the d3 MZ-130? Thanks!

 

[markthefixer]

Hello:
I’ve been scouring threads to identify proper replacement diodes for the sx-1280 protection board with no luck. Can anyone suggest suitable replacements for D1,D2, and D3 on the awm-123? Does the 1n4148 work for d1 and d2? What about the replacement for the d3 MZ-130? Thanks!View attachment 2619188

yes, D1 & D2 can be the 1n4148
D3, 13v 0.5w zener diode

512-1N5243B Fairchild 13 V, 0.5W Zener 0.17 ea
or
78-BZX55B13 vishay 13 V, 0.5w 2% zener 0.23 ea

your choice....

 

[Craftsman11]

ahh, thank you Mark! I had the 1n4148 in stock and will order the 512-1N5243B.

One more question for now: D7 and D8 on the Power Supply Board (AWR-157) call for the On Semi 512-1N5257B which is of course obsolete. Fairchild has the 78-1N5257B which has similar specs except the Zener current is .1uA vs. On Semi's Zener current of 3.8mA. Any suggestions for the proper substitute for the ON 512-1N5257B? I figure I might as well replace if possible since I have it cracked open. Cheers! Now off to my root canal.

 

[markthefixer]

ahh, thank you Mark! I had the 1n4148 in stock and will order the 512-1N5243B.

One more question for now: D7 and D8 on the Power Supply Board (AWR-157) call for the On Semi 512-1N5257B which is of course obsolete. Fairchild has the 78-1N5257B which has similar specs except the Zener current is .1uA vs. On Semi's Zener current of 3.8mA. Any suggestions for the proper substitute for the ON 512-1N5257B? I figure I might as well replace if possible since I have it cracked open. Cheers! Now off to my root canal.

78 is vishay, not fairchild...
78-1N5257B
The Mouser listing is in error. They listed reverse leakage current.
The datasheets say use the vishay.

 

[Craftsman11]

Thanks much. They’re in stock and on order. I really appreciate your help. Have a good weekend.

PS. For you and the gracious others that contribute to this forum regularly—you really are making a positive impact on this planet in many ways. I won’t list them all right now because I don’t want to get too sappy. Cheers!