Curtis-Mathes Stereo

[cadman]

Thanks for the compliments guys- and way cool phone ; ) I can't take credit for the audio circuits, they are a newer design by a guy named Rozenblit, though the power amps originally called for Magnoval base russian tubes that were nothing but trouble, cracking and going to air. They were rated for 150w output PP. I modifed the ckts for 700v plate and 400 screen IIRC and used EL34s pushing them to their absolute limit. Everything that's computer controlled (including the 12 pages of code loaded into the microprocessor) are my handiwork, and throwing the active EQ into the mix worked out well. The eye tube is a 6AF6 and is a stereo version so you can monitor both channels at once, but it's more for grins than anything. A 12AX7 under the chassis behind that tube is the amp stage for it, and there's a gain control on the back. Etc. Etc. Talk about a long and time consuming project!! Never again ; )
Cory

 

[tolivac]

Cadman:Wow!! 700V for plates and 400 for the screens-Thats is pushing the EL34 to the limit. what sort of tube life do you get?The EL34-the workhorse of the Hi-Fi and audio amp industry.Those tubes also make good modulator drivers in AM transmitters as well.Gates,Sparta-Bauer,CCA come to mind of Tx builders that use EL34's as mod tube drivers.The EL34 can even pass video and MF RF-Sparta-Bauer transmitters used them in the low level RF stages.Looks like your Amp is a one of a Kind-you must be very proud of it.
Drmitch: Really nice Sears Silvertone Hi-Fi-didn't think Sears would want to sell anything of that caliber.I always thought of them for selling radios,tv, and small stereos.

 

[kenmore1978]

Tube site

Anybody see this site yet?

http://https//vacuumtubes.net/

 

[kenmore1978]

vibrators

Most of the power sections of car radios that used vibrators are being converted to Solid State since th vibrators are realy getting hard to find, and aparently they don't age well, so even ones still new in the box apparently fail fairly quickly.

 

[tolivac]

Vibrators

I used to have and work on those vibrator radios over 30 years ago.Then vibrators were still available and still would work.Nowadays-they would be no longer made and those still around the rubber supports and other parts for the vibrator reed would be stiff and rotted out.That sure would kill the operation of the vibrator.At that time I was experimenting with solid state circuits to replace the vibrator.Found some cicuit designs that did work.the vibrator is essentually an electro-mechanical mutivibrator oscillator circuit.It could be duplicated(in the circuit I was using)a multivibrator cicuit using power transistors.Unfortunately that data got lost with those radios in the Rapid City S.Dak flood of 1972.I would have to imagine today someone must make a solid state plug in "vibrator" today?Haven't worked on radios like those since then.also remember those "0Z4" rectifier tubes used in those radios?Didn't have a filament-was a cold cathode device-and VERY reliable.also seen 6X5-12X5 tubes used as well.

 

[kenmore1978]

solid state

Well, that knowledge has been duplicated, so vibrators can be eliminated. Also, the latest in the old car hobby is solid state ignitions and voltage regulators that are totally hidden in the original distributors and regulator boxes so everything looks tatally original yet has the advantage of modern car technology. And also there's the "quartzing" of car clocks that make them much more reliable and accurate.

 

[kenwashesmonday]

Vibrators, Solid State Ignition, and Clocks

New solid state vibrators are currently available. They plug in the same way so the radio is not butchered. Don't forget to also change the buffer capacitor.
Often, a new-old-stock vibrator can be made to work by carefully cleaning the oxidation from the points with bond paper, then once you get it to start, let it run a while and the points will clean themselves.

I don't understand why so many people in the old car hobby convert to electronic ignition. Why make the car more complicated and difficult to diognose? I drive my '65 Rambler daily and it's no big deal to change the points and set the dwell once a year.

Car clocks, well, I guess I really wouldn't fault someone for converting to quartz, but they don't make the same sounds and the second hand movement is different. These little things are part of the "trip" of riding in a classic car. The original clocks will usually run pretty well with little effort. The clock in my '60 runs well after a simple cleaning, I unplug it when the car sits for weeks.

Conversion is NOT restoration!

Ken D.

 

[kenmore1978]

conversions

"I don't understand why so many people in the old car hobby convert to electronic ignition. Why make the car more complicated and difficult to diognose? I drive my '65 Rambler daily and it's no big deal to change the points and set the dwell once a year. "

I've changed many a set of points in my time and truthfully, it's a PITA unless it's a GM V8 distributor with the little window in the cap

As for car clock conversions, I've often wondered why they don't use the same type of mechanism a household quartz clock uses where the second hand "steps". Instead, the car quartz second hand goes around like an AC powered household clock (which you may have noticed, are virtually impossible to find new nowadays). Some old car owners are lucky in that not al car clocks HAD second hands so "quartzing" doesn't take away from the authenticity.

And let's face it, solid state voltage regulaters keep much better tabs on the voltage than the old mechanical units. I've had to replace more than one wiring harness that burned up because the cutout relay in the regulator went bad and allowed the battery to try and turn the generator into a motor.

 

[tolivac]

I like the idea of the newer solid-state vibrators-and no mods to the radio-thats better yet-you don't destroy the collector value of it and much less work.At the time I was experimenting with vibrators-My conversion had to be wired into the radio.It was too large for a "plug in" the early power transistors and capacitors-and the heat sink-made it too big to fit in the vibrator area.Used the radios case as a heat sink.
I don't think I would want to put a modern Quartz clock in an older car either.Drather have the "charm" of the old one.
I can go along with the reulators. The relay soleniod types can't keep up and can fail if the contacts stick and cause damage to other equipment.But a solid state one shorting isn't pleasent either.