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 General Electric RS17T1 Stereogram
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 Return to top of page · Post #: 1 · Written at 5:37:08 PM on 3 May 2015.
Maven's avatar
 Location: Canberra, ACT
 Member since 23 August 2012
 Member #: 1208
 Postcount: 581

I've been given the guts of a GE RS17T1 stereogram that has been in a shed since the cabinet was "re-purposed" for a TV table about twenty years ago. The owner was an electrician and tells me everything works. The turntable is a Garrard 3000 record-changer, the amp is solid-state but all discrete components, and the tuner is some sort of coil tuner with press-button selectors. Two twin-cone 12" Rola speakers that look to be in very good condition. Output is supposed to be 10w "undistorted".

I have a schematic and location diagram from the old cabinet. I found a partial service manual on Kevinchant.com, but it seems to be missing at least one page.

I'd like to find a complete spec sheet before testing anything.

Also, I'd like any cautionary advice about testing a solid-state amp of this vintage (1967). The circuit looks very like a valve circuit, to my amateur eye, but I understand that S/S components can be less tolerant of poking and probing.

Maven


 
 Return to top of page · Post #: 2 · Written at 7:00:58 PM on 3 May 2015.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 3919

Pity the cabinet is gone; it was good looking model:

http://www.radiomuseum.org/images/radio/general_electric/rs17t1_1390140.jpg

Unfortunately, I don't have any tech data for that model, but somebody here may well do.


 
 Return to top of page · Post #: 3 · Written at 8:35:51 PM on 3 May 2015.
MonochromeTV's avatar
 Location: Melbourne, VIC
 Member since 20 September 2011
 Member #: 1009
 Postcount: 906

Kevin Chant has a version from the 1967 JR Transistor Group 4 book:

http://www.kevinchant.com/uploads/7/1/0/8/7108231/rs17t1-2.pdf


 
 Return to top of page · Post #: 4 · Written at 11:03:40 PM on 3 May 2015.
Maven's avatar
 Location: Canberra, ACT
 Member since 23 August 2012
 Member #: 1208
 Postcount: 581

Yes, that's the PDF that I have - but notice that it begins halfway through a sentence so clearly something is missing.

Agree the model 1 was a stylish lowboy cabinet with those splayed legs, the model 2 less so with the straight legs. I'm guessing they had some problems with the splayed legs splitting if somebody sat on top of the lowboy cabinet - hefty force at 90degrees to glued joint? The legs are the only difference between the two models, and since I only have the front facsia panel (the speaker mount panel) I don't know which model my innards came from.

It could be a challenge to construct a more compact cabinet for the unit. I'm thinking maybe speakers side by side, angled 45degrees each so 90degrees projection offset, below the amp and tuner rack which sets a minimum width of 27".

Still no plan how to smuggle such a thing into the house, though!

Maven


 
 Return to top of page · Post #: 5 · Written at 10:47:57 PM on 5 May 2015.
Maven's avatar
 Location: Canberra, ACT
 Member since 23 August 2012
 Member #: 1208
 Postcount: 581

After basic checks and inspections I hooked this up on the bench. It delivers a really impressive tone from an AM radio signal through those 2 x12" speakers.

The push-button tuning presets operate directly on slugs in five small coils. I think these can be adjusted as with IF coils by a centre screw, but I'd appreciate the benefit of anyone's experience with adjusting this type of preset. A couple of them are dead right for local stations, but the others need re-tuning.

The unit has both input and output sockets for small tip-sleeve plugs. The outputs go in series with the 8ohm speakers and parallel with (I think) 15ohm resistors. Does that resistor value sound right?

The external input sockets cut out the gram input, so it looks like they take the same input level as the gram magnetic cartridge would deliver. If I can build a cabinet to make this unit fit for human society, these inputs could be useful for other audio sources.

As I recall, 1967 was close to the time when the monolithic console radiogram was overtaken by component hi-fi systems to accommodate reel-to-reel and cassette tape inputs plus FM stereo tuners, and separate speaker enclosures.

Maven


 
 Return to top of page · Post #: 6 · Written at 9:43:05 AM on 6 May 2015.
Tinkera123's Gravatar
 Location: Melbourne, VIC
 Member since 5 October 2009
 Member #: 555
 Postcount: 300

Hi Maven,

re ...... "but I understand that S/S components can be less tolerant of poking and probing."
This is not my experience ..... especially with the older dicrete component circuits. However, I believe your comment maybe applicable to IC's ..... where static electricity and heat from soldering etc could cause problems.

General experience with solid state "tinkering" ..... probably a lot safer than 'playing' with valves. ie s/s is low usually low voltage and low current .... provided you stay away from the power supply ...Smile I usually probe the circuit off chassis ground .... looking for transistors in an ON or OFF state. Unlike valve radios, you may find some transisitors in the OFF state when the radio/amp etc is functioning correctly ... ie protection circuits etc..


re ..... "the tuner is some sort of coil tuner with press-button selectors" .... Permeability tuning. Yes, I had an old Ferris car radio with permeability tuning. When I got it running, all stations were tuned in perfectly, so didn't have to adjust/realign ...... but I don't see it as presenting a problem ... just use an insulated, non metallic adjustor eg old knitting needle .... and be gentle in getting the slug to turn.

Cheers,
Ian


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
Cheers, Ian

 
 Return to top of page · Post #: 7 · Written at 2:55:20 PM on 6 May 2015.
Maven's avatar
 Location: Canberra, ACT
 Member since 23 August 2012
 Member #: 1208
 Postcount: 581

I'll be careful in attacking the tuning pre-sets. First I will check whether there are any fixed caps attached to any of those slug-and-coil tuners that might have failed or gone off spec.

There is a manual over-ride tuning knob that was not functioning. It links to the coil/slug array by a friction clutch. The rubber clutch disks had shrunk or lost friction to some extent. Rather than disassemble the whole axle, I folded over a piece of fine sandpaper (rough side out) and cut it to shape with a hole for the axle and a slot out to the side opposite the foldover. This made a double-sided sandpaper shim that I could slide in between the rubber clutch plates to create a firm friction layer. Works fine.
Maven


 
 Return to top of page · Post #: 8 · Written at 4:52:51 PM on 6 May 2015.
Tinkera123's Gravatar
 Location: Melbourne, VIC
 Member since 5 October 2009
 Member #: 555
 Postcount: 300

Hey, now there's a good idea. Clutch thingy was stuffed on my radio also ... just left it as I couldn't see a solution without major effort..... Smile


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
Cheers, Ian

 
 Return to top of page · Post #: 9 · Written at 7:24:10 PM on 29 May 2015.
Labrat's avatar
 Location: Penrith, NSW
 Member since 7 April 2012
 Member #: 1128
 Postcount: 152

Dear Maven.

I have not seen a picture of the push button tuner, but assume that it is adjusted as follows.
Grip the first, (left most) button and pull it towards you. It should come out around one inch.
Then tune in a station near the bottom of the band. Next push it in to store that station on that push button. Then repeat, working your way to the right, and up the dial.

Wayne


 
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