Preamp Deal of the Century

simon:

you might consider buying a cheapie learning remote such as the universal remote control R7G (URC-R7G) and shipping it to someone who has a functioning supratek remote. i would be willing to program the learning remote with my supratek codes if you shipped it to me, but i'm in america. i'm sure there are some supratek owners in australia who would be able to help you out. otherwise, drop me a line and i'll get you my address information. good luck.

Hi Kg,

thanks for your offer :-) I'm actually in the UK.
I picked up a couple of cheapo universals but they only
provide for a 3 digit code.
I will try and find a universal that takes 5 digits.
The problem as far as I can see is that the learning remotes seem to depend on them being able to power down the
unit as they trawl through the codes which might make it awkward.

My remote was working to increase the volume but not the other way. I opened it up to try and fix it and now it doesn't work at all :-(

Cheers Simon

HI Guys,

Don't know if anyone is keeping up with the thread anymore, but I have a problem with my Cortese and I was wondering if anyone might be able to help.

I am getting a spitting static noise through one channel. I have fliped all the tubes and the noise still comes through the same channel. I have a friend looking at it now. He thinks it is one of the adjustable resistors in the line stage. He replaced them, but there is still noise in the same channel. He is going to check connections in the power supply next. He has already checked connections in the preamp and they seem to be ok.

Does anyone have any ideas?

Thanks,

Tom

IMHO,

When the usual hit or miss tube swapping troubleshooting technique fails, you have to have a freq generator and a scope to solve problems like this. This is not just a matter of what "looks" broken anymore.

Your tech friend, how did he come up with the decision of replacing the resistor first?

Tell him to isolate the PSU circuit to the actual amplifier circuit. By feeeding very low freq signal at the input, you can tell if the power supply is the one with a problem looking at the modulation, if any, of the B+ signal. At mid to higher frequencies, you could test the real amp section stages by stages, assuming that the usual downstream B+ voltages checks out as it decrease when being decoupled from the stages, and see where the noise is coming from.

Please ask your tech about those. If he does not understand what you are talking about, find a different tech. It would be helpful also to plot the schematic first before poking around with the scope so that you can easily follow which point checks out in relation to the diagram.

Hope it helps......

ADDENDUM

My post above assumes that you already tried swapping amp, speakers etc. and the problem is in the linestage. If phono, and using a 6106 rectifier, I would take a look at the FET for that particular channel. The 6106 have a voltage drop of 60V, and a maximum dc current output of 125 ma. The 5AR4 on the otherhand is 17 and 250 mA. As you can see, the preamp is being starve not only with the voltage but also of the current when using a 6106. Since transistors are current driven, I would take a look at that first if it was me but using a 5AR4 rectifier.

I seem to remember that Mick was frustrated about units that was shipped back damage from using 6106 tube in the PSU before. IMO, it is possible that what i described above could be the reason.

I could be wrong of course ......