Tube Stereo Consoles from Thrift Stores

[planet10]

Turns out my Fleetwoods differ slightly. The biggest difference is that one has way bigger OPTs -- and a bit of weird circuitry on the input of the power tube. The one with the smaller OPTs -- still substantial for 50EH5s -- is a Baycrest. This one has the same OPTs as Giovani's.

The amp is actually Japanese, and much more neatly constructed than the typical North American or German units.

dave

[planet10]

Here is the essentials of the circuitry... with only a requirement for 2.5V to reach full power the 12AX7 is way overkill (and may partially explain the large gridstopper). The grid leak on the power tube is one of the tone control pots.

dave

[planet10]

And here is the minimalist design i'm hoping to get away with... no grid stopper, wired in triode (lower power, lower output resisitance), no cathode bypass (some degeneration, higher output resistance). If i can get away with it, then the only cap in the signal path is the last power supply cap.,,, with only a requirement for 200V i can put a nice poly there.

dave

[gmilitano]

Originally posted by planet10
And here is the minimalist design i'm hoping to get away with... no grid stopper, wired in triode (lower power, lower output resisitance), no cathode bypass (some degeneration, higher output resistance). If i can get away with it, then the only cap in the signal path is the last power supply cap.,,, with only a requirement for 200V i can put a nice poly there.

dave

This looks great. I'd be willing to try this out too. When you say poly, are you talking polypropylene or is polyester good too?

Is that 6CA4 tube of any use in a power supply.

I am also interested in a preamp. Can the ECL86 tubes be used for that?

Cheers,
Gio.

[planet10]

Originally posted by GG
This looks great. I'd be willing to try this out too. When you say poly, are you talking polypropylene or is polyester good too?

In general polypropylene is better.... If i don't have something suitable in my collection, i'll probably just get a Solen.

Is that 6CA4 tube of any use in a power supply.

Yes... we have been having good results with EZ81 -- been using them in hybrid bridges to replace SS bridges,

I am also interested in a preamp. Can the ECL86 tubes be used for that?

There is a thread somewhere here on this forum about just such a beast.

dave

[gmilitano]

Just for fun, I decided to power up the two old consoles. A little to my suprise, they still worked! Some of the capacitors must be dead as you get clicks and pops. I did get a kick playing an mp3 player through them. The radio sounds very good!

Other than the audio tubes and iron, what is worth salvaging off of these consoles? Are the radio tubes worthwhile to hang on to? I imagine the electrolytic caps will be close to dead. Are the carbon comp. resitsors worthwhile to pull, they are mostly silver tolerance?

These capacitors caught my attention .. they look like some sort of poly.

Gio.

[planet10]

Originally posted by GG
Other than the audio tubes and iron, what is worth salvaging off of these consoles? Are the radio tubes worthwhile to hang on to? I imagine the electrolytic caps will be close to dead. Are the carbon comp. resitsors worthwhile to pull, they are mostly silver tolerance?

You never know... i save everything i can strip out that isn't obviously pooched... i'm often surprised at what is useful (or saleable).... pull those drivers -- even if it is only for me to see a pic

dave

[gmilitano]

Hi Dave,

Any thoughts on those capacitors? The outside feels like ceramic?

Sorry, with only one good driver I did not bother pull the speakers. I will take pictures next time.

I think I may go hunting for more consoles this weekend. I'd still like to get some more parts for a phono amp as I am not sure about an ECL86 phono amp. Do these consoles ever contain any sizeable chokes?

As for the 50EH5 tubes, I'd like to try a small wattage amp which I would use for the office since I have to play music very quietly.

I have been playing around with PSU Designer II...very nice, I can't wait to build a powersupply using an EZ81. Is there something similar available that would help me design an amp or preamp?

Regards,
Gio.

[planet10]

Originally posted by GG
Any thoughts on those capacitors? The outside feels like ceramic?

I'm not quite sure what those are... Aerovox is a good brand name thou.

I don't think i've ever seen a choke in a console hifi.... organs thou are often quite rich for power supply bits.

dave

[gmilitano]

Originally posted by GG
I have been playing around with PSU Designer II...very nice, I can't wait to build a powersupply using an EZ81. Is there something similar available that would help me design an amp or preamp?

I took a look at SPICE, but it looks too complicated. Can someone suggest any other tube design software? Is TubeCAD the only other choice? The price sure looks ok if it does what it claims to do.

Regards,
Gio.