Thurbly Thandar Instruments (TTi) PSU quality ?

[BravoV]

At work now.  All the caps were ELNA rated at 85 degrees.  I replaced them all with a mixture of Rubycon and Panasonic 105c, cost more than I got the PSU for! 

Hmm.. I thought ELNA supposed to be decent brand ? Say compared to CapXon ? 

The rectifier caps went to the junk box, the others to bin. 

Geezz... what happened ? Leaked too ? ELNA ? 

Btw, does your rectifier/driver board with those bulk caps looks the same as mine ?

Looking at my notes, the bad cap on both channels was 220uf 10v.  I put a 25v on in its place, which was slightly too big to fit correctly.

Yes, noted and spotted, its C37 as the schematic, and its CapXon GS series with 85C rated, thanks for the highlight. 

As stated, definitely I will replace all elcos both at the master and slave control boards, although haven't decide on the driver board yet. 

2 out of the 4 LED displays on mine had bad segments, the displays are an old standard size.  I bought replacements on ebay, they were not an exactly (visual) match, the 4 digits are made up from 2x2 digit units, but were otherwise compatible:  NSC NSB-5881 Multilexed DISPLAY RED LED MODULE 4-DIGIT 7 SEGMENTS Numeric 0.5INCH

The led dies in the displays are bonded directly to the PCB, with just the plastic cover as protection, so are exposed to damp. The bad displays were both voltage, so near the leaky capacitors...

Queried ebay, all gone. But I can live with it right now, while searching for alternatives, maybe to replace the whole LED board with custom PCB and use standard sized ones and still using the red plastic cover as above photo.

BTW: I think the designer of these (or some versions) is a forum member.

Who ?

BBTW: Does anyone have an cheap source for the ALPS pots, they are a old size. Mine were dirty but improved after cleaning, on seconds thoughts replacing them with multi turn pots would be a better solution.

Mine also abit scratchy, especially at the current pot, does yours look like these ? Attached below shots of the log taper current pot and two linear taper for coarse & fine voltage pots.

[BravoV]

I agree that you don't need multi-turn pots for the current limit. Do you see R48 in parallel with the current control VR5? This gives it an interesting logarithmic-like taper, making it easy to dial in a small current limit but still providing the full range on a single turn part.

Its a logarithmic taper for the current adjustment potentiometer as above attached photo.

Yes, its quite unique feel when using the current pot, fine adjustment at low current while getting coarse at higher setting.

You seem keen on fixing it up, so you might care to know that you can likely remove the yellow patina from those knobs using high strength peroxide and sunlight. Google retrobright, and check out some posts like this and this in another thread, where member TiN and I each restore front panels of expensive Keithley 2001 meters. As they are now, those  yellowed knobs are a real eyesore.

Thanks & wow .. thats impressive results on the panel work, especially for the dings. 

The ingredient of sun light + soaked inside a hydrogen peroxide solution should be enough right ?