Hello, all...
Not antique (apologies to radio+phono NG) but I'm looking at a naked,
unknown AM/FM tube chassis, circa 1960's. It has no brand name and is
a AC/DC unit (series heaters, live chassis.) I'm trying to figure out
if it is worth restoring, breaking up for parts or just dumping (the
latter is tempting!)

Anyway, I'd appreciate the group's forensic opinion, e.g. any info as
to what brand it is and, of course, any leads as to the schematic.

Here's a few details:
Tube line up (assuming in correct sockets):
17EW8 (didn't test - no details)
Two 12BA6's (both test "good")
12BE6 (tests "poor")
One missing 7-pin tube - type not known
19EA8 (Both sections test "poor")
Audio: 12AX7 (Both sections test well into "good")
Power output: two single-ended 50EH5's (Both test just into "good".)

The 19EA8 and 12AX7 are on a PCB above a large square hole in the
chassis. All the rest is point to point wired.

The tuning capacitor is a typical dual 300/500 pF, or so, AM type,
plus a dual 50 pF (guessed) FM type on the same shaft. Dial cord and
pointer are connected and actually work!

The two (stereo) small output transformers are a bit odd - they appear
to have 4 wires on the primary, 2 go from the 50EH5 plate circuit to
B+, of course, but 2 more are connected into the 50EH5 cathode circuit
(I think.) I've never seen this before. NFB? These O/P transformers
are both stamped "AT-18J, 0 - 8 ohms" The 8 ohm secondaries are
totally unconnected anywhere in the circuit, rather appear to just
take speaker connectors (missing.)

On this chassis B+ must be quite low, less than 150 VDC is my guess
(based on capacitor ratings of 180 VDC), so this radio puts out a
little over 1 watt per channel, maximum.

Other chassis markings are "JAPAN" and IFT's are marked variously
RT-71, RT-54H and RT-49.

There appears to be a 1/2 wave solid state rectifier under the chassis
(about the same shape as a disc capacitor and about 1/2 inch in
diameter.) There's no tube rectifier in sight!

That's about it. All replies welcomed.

Cheers,

Roger
--
Roger Jones, P.Eng.
Thornhill, Ontario,
Canada

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"Engineer" wrote in message
...
Hello, all...
Not antique (apologies to radio+phono NG) but I'm looking at a naked,
unknown AM/FM tube chassis, circa 1960's. It has no brand name and is
a AC/DC unit (series heaters, live chassis.) I'm trying to figure out
if it is worth restoring, breaking up for parts or just dumping (the
latter is tempting!)

Sounds like a typical Hitachi or Panasonic chassis of that era. Missing tube
is likely a 12AT6, or 12AU6/12BA6, depending on where it is in circuit.
Identifying marks that could be useful would be on those IF cans or output
transformers. If it's a Panasonic chassis, there will be a three pointed
star made of diamond shapes. If it's Hitachi, it will be a circle with lines
through it. This would also be seen on any original tubes.

"Brenda Ann" wrote in message
...

"Engineer" wrote in message
...
Hello, all...
Not antique (apologies to radio+phono NG) but I'm looking at a
naked,
unknown AM/FM tube chassis, circa 1960's. It has no brand name
and is
a AC/DC unit (series heaters, live chassis.) I'm trying to figure
out
if it is worth restoring, breaking up for parts or just dumping
(the
latter is tempting!)

Sounds like a typical Hitachi or Panasonic chassis of that era.
Missing tube
is likely a 12AT6, or 12AU6/12BA6, depending on where it is in
circuit.
Identifying marks that could be useful would be on those IF cans or
output
transformers. If it's a Panasonic chassis, there will be a three
pointed
star made of diamond shapes. If it's Hitachi, it will be a circle
with lines
through it. This would also be seen on any original tubes.

You may be right but there's no logo of any type to be seen. BTW, the
tube brands are all "Fleetwood". The missing tube is definitely an IF
amplifier, 7-pin, presumably a pentode.

I've found a couple more markings on the chassis. An ink stamp "8
67" (Aug 1967?) and what might be a model number stamped into the
metal, viz: "51F092". The serial number is ink stamped as "4588".

When I get the time I'll do some circuit tracing...

Cheers,

Roger
--
Roger Jones, P.Eng.
Thornhill, Ontario,
Canada

Anti-spam... Reply to: SurfNews"at"sprint"dot"ca (but written
correctly)