TT Phihong PSM-5341 repair and recap

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Joined: Fri Sep 15, 2017 11:49 am

TT Phihong PSM-5341 repair and recap

Post by Steve »

Been working on this for a customer, said his TT would just randomly shut down with a 'wheeee' noise and then refuse to turn on. Sent it to me and under testing sure enough it would turn on for 5 seconds and then shut down. Wasn't sure exactly to the cause so I started with a full re-cap, which didn't fix the problem.

After inspecting the underside of the PCB I noticed the usual track cut from the factory wasn't 100% done properly, so I cut the trace fully and retested. But no it still showed the same behaviour.

I then suspected the opto-isolator because I've read that the trace cutting is somehow related to it, so it's possible it could have died due to the trace not being cut properly. So swapped it out for the proper Sharp pc-111 (because it had the 'bad' type) and voila, it now works perfectly :)

Before re-cap:

PXL_20210629_094134429.jpg (389.88 KiB) Viewed 1160 times

After re-cap:

PXL_20210629_101111676.jpg (411.89 KiB) Viewed 1160 times

The almost-cut trace:

PXL_20210629_101751254.jpg (362.03 KiB) Viewed 1160 times

Swap opto-isolator:

PXL_20210629_105556074.jpg (338.25 KiB) Viewed 1160 times

New opto:

PXL_20210629_105815859.jpg (338.34 KiB) Viewed 1160 times


PXL_20210629_111122380.jpg (410.9 KiB) Viewed 1160 times


PXL_20210629_111133593.jpg (409.69 KiB) Viewed 1160 times


PXL_20210629_111147239.jpg (413.1 KiB) Viewed 1160 times
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Location: Co. Durham, UK

Re: TT Phihong PSM-5341 repair and recap

Post by thesofa »

Thank you so much for an excellent job, first class fast service and good comms.
Cheers sir
TT030 with Storm with 256 Mb Ram, Thunder with a CF drive and Lightning, HxC floppy emulator and one of Codekiller's magical Mono/Colour switchers, also 3 STS one has TOS1.0 AND 2.06 switchable with an HD drive, the other two are untested as yet, just bought for spares!!
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Re: TT Phihong PSM-5341 repair and recap

Post by rubber_jonnie »

Nice one, and you've just reminded me, I think need to order opto isolators for my Mac Classic.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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