And while I am waiting for the main caps to turn up, I decided to finish up as much as possible on the QRX3000.
The 3000 is also a nicely put together unit too.
Whopping great 15 watts per channel from a quasi cap coupled design.
There were issues with one of the amp channels, when I put it all back together I began to go through and set the bias.
This all went very well until I got to the Left front channel. NO bias. So I chased my tail around for a couple of hours head scratching, it was definitely on the driver/amp board, but i just couldn't find it.
ALL transistors measured good. ALL resistors were good, caps all in the right way, I thought I was going mad...
THEN, I measured point to point through the output transistor and this was telling me the transistor was OPEN.
So I immediately thought broken track, I could not find a broken track!!
I had the amplifier idling with the meter on the emitter resistor looking at the NO bias current, and I just happened to press one of output transistors and it all burst into life, so to cut a long story short, one of the legs of the transistor had become detached from the internals of the transistor, the leg was loose.
Of course these TO218 transistors are not something I have lying around, everything I had in TO220 (essentially the same) was too fast, these little things are 4mhz, everything I have lying around is 30-100mhz...
BUT I had some Sony 2SD313 lying around which were taken out of a working regulated power supply, they actually fit the bill perfectly so I used them.
Then I aligned the tuner, which obviously had never ever been touched, so not a lot was needed, just a little dial calibration and RF tuning calibration.
Interesting that this particular tuner has a 67khz SCA sub carrier decoder!! Something which was used in the 60's and early 70's....pretty cool to see that.
So this one is all ready for its new Main Cap now.
My policy has changed regarding main caps, I have seen two leaking main caps in the last few units i have done, time is marching on and I think every living electro cap needs replacing now, they're all time bombs in my opinion.
Some pictures...