hifi engine

sansui g9000 mint

rodder's picture

So i gust got my first sansui g9000 from the owner who bout it new. It all works perfect in mint condition has never been worked on so here the deal other than a lite dusting and some dexon should i recap? And if i recap what easel should be done? Or will recaping lower the value ? Because it still all stock as it came new untouched and working payed 800 cash tell me what you think and why( note ! My plan is to keep it and use it from time to time )

sansui g9000 mint

The Unit is from around 1978, and if it is mint and working 100% as you say, why mess with it?

While many believe in wholesale replacement of all caps, I do not, especially seeing these original in your unit have been working fine for 35 years. Not sure the replacements would be as good quality wise, and last as long.

what I do when I get a unit is test before replacement
Disconnect 1 side of the main filter caps and test them with a cap/esr meter (Peak Atlas meter). If the value is in tolerance (rating is usually 20%) I usually leave but prefer + or - 10%. But your unit has cap pairs (2X6800) in each can. I would make sure that they are within tolerance, and that each pair are similar value. If they all look fine, I would leave them. If any are bad, I would replace in pairs. If more than 2 are bad, I would replace them all.

I would then test voltage on the input and output of each board other than driver, making sure that there isn't any excessive DC present. compare from left to right of the board to see if it is the same. 5mv or less is usually fine. This can help find leaky caps

I would then remove a few of the small signal polarized aps (1uf, .47, .22, 4.7, etc) and test them using a cap/esr meter. Look for high values (1.5 times rated or more) and ESR reading of greater than 3 to 5 ohms). If some of them are looking bad, you may want to replace all similar types on that board, and others that use the same type. The ones that seem to get this issue are the small caps that couple one part of the circuit to the other. Filter caps that are connected for DC to ground usually are fine.

I then turn on the unit let it warm up, and check the DC bias and DC balance. If they are fine and stable, I usually don't replace anything other that the first electrolytic cap on the board (usually a tantalum rated at 1uf or less). If I get DC balance, or DC bias that is tracking up and down, not stablizing, I replace the initial small signal differential amp pairs of transistors on the board. But on this unit, I would replace the second pair (2sc1775's) as the first pair are FETS and usually don't get noisy.

I replace caps on the regulator board if there are any that show signs of overheating such as bulging, or that the plastic cover has shrunk down. I usually replace the regulator transistors with more modern ones rated at 6amp rather than 3amp.

Last but not least, I remove the speaker relay, disassemble, clean the contacts and reinstall.

Hope this helps