Admiral stereo multiplex console

[DavGoodlin]

1963 model Y4751 - Picked up this treasure yesterday, had to finagle it down from a 3rd floor attic, ad was on craiglist for a month.
As many keywords that bring up additional listings, there are new ones like "chest stereo" etc.
Condition is not great due to some missing veneer chips and general wear issues. I'll be on that. I want this one inside the house for a while.
Its just like this one; http://vintagehifipgh.com/forum/index.php?topic=1533.0
Pictures coming but Id like to make it look this good first.

Of course it was already plugged in when I got there and the FM boomed well despite the scratchy pots and, considering how fuzzy it was inside, it has few Admiral tubes. All screws were holding the back on, a good sign. Chassis plugs and wiring harness appears to have never been moved.

The record changer is an actually not a V-M but an Admiral-Ensign, using a ceramic cartridge. It spins but I took it out for the usual going-over before i even try it.

The 3PA8A amp chassis is the power supply also. A 5U4 and two single-ended 6BQ5/EL84 tubes each drive 12-inch woofer and two 3.5" HF paper-cones (like RCA tweets). Not a great deal of power but it will be interesting to compare it to my Philco Stereophonic that drives one center wooferform a third output transformer using same SE output tubes.
Need to replace the paper caps (white ceramic) and at least test the multi-section electrolytic.

The 9M1 pre-amp/tuner is pretty interesting and includes a 6FG6 tuning eye, 6C9 FM osc-converter, 6AYll dual diode/triode and 12AU7 for the multiplex. There are few suspect caps on this chassis.

[Electronic M]

A college friend of mine uses the guts of almost the same model as his tube audio system. They sound good with a good pair of book shelf speakers hooked up when they are working right. I recommend changing the white tubular ceramics and bumble bees in the audio amp chassis...I helped my friend do that and the improvement was quite noticeable.

[DavGoodlin]

The threads on AK indicate the limiting factor in this unit is the speakers, despite their appearance.
It's surprisingly good sound for a single-ended amp alright.

I once found an Admiral amp chassis in a dumpster that had parallel push-pull (that's four) 6BQ5's

[DavGoodlin]

The amplifier in this unit sounds a bit better and gets louder than the Philco with the same SE 6BQ5 outputs.
After a recap of the tuner and amp chassis, both AM and FM function pretty well.

Funny thing about the tuning eye, it does not open up with no signal but is closed until a strong station is tuned in, then it seems to overlap. Time to check some resistors there...

One issue has emerged after its playing 10 minutes, a background strange hiss-crackle starts up, reminiscent of IF transformer silver-mica disease.
The strange part is that, while it varies with the loudness setting, its present on AM, FM and Phono settings. This seems to clear the IFTs.

Without a schematic and freeze spray, I can't investigate much.

Time to work on the record changer next.

[DavGoodlin]

I got lucky buying a ton of tubes a few months back that included the two that fixed the tuner-preamp chassis problems.

Replacing the 6FG6/EM84 tuning indicator "opened it up" on a no-signal condition. I was sure that if the eye did not open, a resistor was to blame but the voltages measured right on. Now it bounces between stations like a German radio does, closing only on the strongest FM stations.

The hiss was narrowed down by tapping the compactron pre-amp tube 6AY11 (dual triode - dual diode) and freezing everything around it. Fortunately, the pre-amp input RC integrated clusterf**k was not the problem, just the 6AY11 was. Now it plays for hours with no issues.

The last item to fix was the record changer, an Admiral-built unit with a Sonotone 9T cart. The platter ball-bearing cage was removed and old waxy lube in the race was dissolved with turpentine. I re-lubed it with lithium grease. The remained of the parts and motor were lubed with light sewing machine oil. After working the cycle wheel, it played and changed records without slowing. I ordered a new stylus though the existing one seemed to play my worn-out shop records pretty well.

The amp chassis should have a 2 amp fuse for the entire set.
I added the fuse holder into an existing hole, accessible with the back cover on.
I also replaced 2-Y1 safety caps from either side of line to chassis.

As I may have said before, this amp really sounds like its a push-pull but has only one 6BQ5/EL84 for each channel.
It may also be the last tubed Admiral Stereo console, with not a single diode or transistor in it.
Now its time to bring it in the house for some stacked-record endurance testing before I try to sell it.