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Astrosonic and Other SS Magnavox's / 1964 Magnavox 2-ST677
«  Bill May 03, 2021, 07:12:41 AM »
Good job Trevor!   It sounds goods so you should not have any trouble selling it. 

Astrosonic and Other SS Magnavox's / 1964 Magnavox 2-ST677
«  TJ May 02, 2021, 09:02:08 PM »
Here it is all up and running: https://photos.app.goo.gl/u4qAt489obvPd7GNA

What you hear when I get to the AM band is the power adapter for the bluetooth interfering. 

Time to put the back on, polish it up, and get it sold! 
Electronics / Transistors and substitutions
«  Motorola Minion May 02, 2021, 06:35:01 PM »
I agree that SS can be a royal PITA when looking for transistors.

Whenever a Magnavox has transistor issues, its not too hard to figure out. The circuits are very conventional and of course, not complicated like direct-coupled stages of Japanese high end units.

My Dynaco ST-120, QS-300 and SCA-80 are not simple but they are easy to work on and not very fussy about replacement parts.
Wanted / Maggie volume control
«  hermitcrab May 02, 2021, 04:51:10 PM »
Well at least you got quick service from Mark... the reason I made my own?.... because Mark kept on forgetting the one i asked him to build for me like for 2 months ... so I told him nevermind and built my own
Electronics / Transistors and substitutions
«  Bill May 02, 2021, 04:05:48 PM »
That's good news on your Astrosonic Trevor.  We all like to hear success stories and one of these days I will write about what I have been up too and how it all came out.   

Electronics / Transistors and substitutions
«  TJ May 02, 2021, 10:50:07 AM »
The 1964 Astrosonic that I recently redid sounds great, all germanium, and needed a full recap. 

The 1969 Zenith Z906, all silicon, full recap, likes to blow the output transistors...  Everything checks out correctly, I'm guessing there is a short somewhere that is over biassing the transistors. I've given up on it. 

My two mid '70s receivers that I have both had transistor issues, the Pioneer SX-750 has a 2-in-1 transistor that notoriously likes to fail, and there is no easy replacement. I was able to find a working pull on ebay. The Kenwood Kr-7600 had a bad filter cap and a bad bridge rectifier.  Both receivers got a full recap and sound great. 

For me, the tube equipment is much easier to fix, straight forward, easier to find parts for.  I dread older solid state equipment that is listed as not working as theres always the chance of a bad, unobtainable transistor...
Electronics / Transistors and substitutions
«  Bill May 01, 2021, 08:05:37 AM »
As for me, I have avoided SS stuff like the plague.  Not sure why, maybe because I'm still trying to learn tube stuff.  I think what really scares me is the PC boards and all those tiny little solder joints.  Maybe someday!

Electronics / Transistors and substitutions
«  Motorola Minion April 30, 2021, 03:39:30 PM »
By 1968, solid state equipment manufacturers "transitioned" from using Germanium to Silicon devices. As a result, DeOxit, new caps and an occasional resistor are on hand for any solid state repair of non-IC stuff.

This silicon was found even in most common equipment by the 70s, making repairs on older and cheaper solid state stuff (Silvertone, Airline, etc) dicey at best. I learned the hard way by recapping some easy-appearing ones and barely improving the crappy sound. Lastly, it was not worth replacing all of them if not one or two defective transistors.

But some older Germanium transistors still perform such as the RCA-made devices Zenith and Magnavox also used, making a recap generally a slam-dunk.

I think most of us here favor tubes and will dive with confidence into any repair on tube equipment ;D

But having said that, I welcome your opinions and experiences on this matter.
Wanted / Maggie volume control
«  Bill April 29, 2021, 06:55:58 AM »
Looking at what Elton and Chris posted on my thread reminded me that I did not post that my new volume pot arrived from Mark Oppat.  It looks good, not sure if it's new old stock or something he built as it has a Centralab sticker on it.  I have yet to install it, but that might happen today. 


Wanted / Maggie volume control
«  TC Chris April 28, 2021, 09:14:04 PM »
Great concept with the lock graphite.  I wonder if epoxy glue would work?  Maybe more durable in higher temps?

Now apply your creative thinking to this one.  I was working on a CD player and, in one of those fits of stupidity that seize me from time to time, I managed to break the plastic ribbon cable that connects the laser head.  A flat plastic film with lots of little skinny conductors across it.  There must be some work-around.

Chris Campbell
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