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-   -   Cool Sylvania Receiver- Believe it or Not! (http://www.diyaudio.com/forums/solid-state/184065-cool-sylvania-receiver-believe-not.html)

mikje 27th February 2011 08:31 PM

Cool Sylvania Receiver- Believe it or Not!
 
6 Attachment(s)
I Picked up this beauty for $10. It needed a cleaning inside and out, but now it's playing tunes quite nicely. Something a little different though; many of the transistors are in sockets. They all needed a good de-ox. They slide right out, which would be nice for trouble-shooting, but I don't know about how well they'll stay in place over time. Some aren't in very firmly. When I first fired it up, it was nothing but loud, crackly NOISE! Both channels had sound regardless of where the balance was. I cleaned all the controls, pots, and transistor sockets and now she sounds pretty good.

It's got a switch for the phono input for selecting a magnetic or ceramic cartridge. The output transistors are one 13-36443-1 and one 13-36442-1 per channel.

One problem I'm having with it is that the volume isn't the same on both channels when using the tuner. It's quieter on the left channel. I switched to mono and the volume is the same. It's OK when using the aux input. It's only an issue on the tuner in stereo.

The bulbs are burned out, but I think I need to switch it over to LEDs anyway. The plastic housings around the bulbs are melted and the contact paper on the case is dried out above the bulbs. The voltage at the bulbs is 4.7 VDC. Any info on how to switch it to LEDs?

Thanks for indulging me!
Mike

indianajo 27th February 2011 10:10 PM

If the light bulb supply is AC. you'll need a bridge rectifier. If you use 10 ma LED's with no internal resistors, you'll need about a 300 ohm resistor for each. If you cut up a string of 60 white LED christmas lights, I think that works out to about 3 V apiece so they might have internal resistors. 1.6V loss in the bridge, +3 V per led, works out about to 4.6V. There are replacement LEDs at the dollar store around Christmas. Otherwise you have to buy something from an electronics supplier. Regular red/green'yellow Led's drop about 2 V.
Chasing unbalanced channels involves a scope. L versus right. On my PAS2 with that problem, I swapped tubes L-R no improvement, replaced the electrolytic caps, no improvement (they are always dried up after 25 years) then started swapping paper caps. The last one out of twelve had the burned spot in the wax shell allowing the air to attack the paper. Well hidden by the ****** that constructed it. You may have a loose transistor, differently aged electrolytic caps, a bad solder joint, or a bad pot somewhere.
I've got a legendary Dyna FM3 tuner but it never picked up the weak classical stations very well. Forty years after bankruptcy in this day of the internet, the alignment instructions and schematic diagram are still something you have to pay for. The best stereo tuner I ever had was a $10 GE pocket radio, just replace the headphones with an adapter cord and put in new batteries occasionally. But I knocked it off the table and broke something. Replaced it with a $35 Sony pocket radio; it's sensitivity is **** and it has a digital synth howl. Now I am using a mono table all-band radio with new electrolytic caps that my father bought from Reader's Digest in the seventies or somewhere. Decent sensitivity on FM but the sound is mediocre. It has a 1W amplifier that is capable of driving a Peavey SP2 speaker to decent volumes, which is cool since the 1998 Peavey CS800s blew a circuit breaker last week, and the djoffe bias CB (not printed) in the ST120 broke a solder joint or something and is running the output transistors on one side hot. I may need to break down and draw up a circuit to make Djoffe mod PC15 PCB's for the ST120, since he is not going to. The cs800s gets new Power supply caps before I start any scope debugging. Caps might have taken out the switcher FET.

destroyer X 27th February 2011 11:49 PM

Oh!....i am feeling envy...i love this kind of stuff
 
Thank you by the pictures...this reduced my envy as i have enjoyed watching it too.

regards,

Carlos

kipman725 28th February 2011 06:55 AM

no need for a rectifier for the LEDS as they are diodes and so half wave rectify on their own.

destroyer X 28th February 2011 09:43 AM

Yes...no need of rectifiers and filters..... only a resistance can do the job
 
but, of course... DC will work too....it is an option, to use the simplified version (AC) as a shortcut or to rectify the whole thing.

regards,

Carlos


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