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 Post subject: Re: My Son brought me a present. Anyone know about this
PostPosted: Feb Tue 12, 2019 1:04 am 
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Joined: Dec Sat 24, 2011 9:17 pm
Posts: 3619
Location: Vancouver Island, Canada
SpiderLovesBeer wrote:
Hey John. Can you break that down a little more for my experience level??
I know it has to be something simple but I just don’t understand how to test things yet.
What to test, how to test I have no clue.
The 1st page of the schematic shows two views of the band switch. You say the phono has audio and you can turn it off. Correct me if not.
My thought from 3000 miles away is that the band switch contacts are tarnished, except for the position it has been in for years while it sat.

To test for plate voltage-. The Plate of the tube is illustrated as a flat bar usually the top bar in the tube diagram. So the + lead of your DMM is clipped with an alligator clip to the pin corresponding to the plate. The most negative point in the circuit is the negative end of the filter caps.
If that is also chassis ground, you can clip the negative lead of the DMM to the chassis or a ground point.
The actual voltage is not critical but good to know.

Clip your + lead of the DMM to the plate of the AM detector tube 6BE6 pin 5. You should see some significant voltage there, 100 vdc.
Turn the bandswitch to the AM position and find the grid of the 6BE6 tube, pin 7.
You should hear sound, hum or crackle at the speakers when you touch the grid with a probe, wire, screwdriver or finger on stem of screwdriver.

The FM detector tube is 6U8. You should read a DC voltage on pins 1 and 6. The grids are pins 2 and 9.
This tube is a 9-pin duo-triode, two tubes in one envelope.

Use the higher settings and these are high voltages so turn off between tests. Avoid snapping power off and on rapidly.
This is a start at diagnosis.

_________________
Watch the doughnut, not the hole.
Burl Ives, RIP, oldtimer.
[:l>)


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 Post subject: Re: My Son brought me a present. Anyone know about this
PostPosted: Feb Tue 12, 2019 2:22 am 
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Joined: Jan Tue 31, 2012 1:55 am
Posts: 7303
Location: Mountains of Mourne. Ireland.
Tube pins, as mentioned by John.
Image
Image

Tube pin numbers can also be seen on the schematic.

For the above pinout diagrams - see pdfs
6BE6 http://www.r-type.org/exhib/aaa0011.htm
6U8 http://www.r-type.org/exhib/aaa1219.htm

------------

For radio schematics...

F filament
H heater
P plate aka a anode
K cathode
G grid
S shell (metal)

NC no connection

Greg.


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 Post subject: Re: My Son brought me a present. Anyone know about this
PostPosted: Feb Tue 12, 2019 6:40 am 
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Joined: Sep Mon 24, 2018 5:30 am
Posts: 236
Location: Wilmington Ca
Thank You Guys so much. This is what I needed. I put Her all back together and was going to wait until I understood a little more. I’ll tear Her apart tomorrow after work and do as you guys suggest.
I need to get 2 caps though. I’m still learning so I sniped C63 & C63 before reading the schematics.
I’ll never do that again. 1400kv
Wow.... live and learn
I’ll be back soon with an update.

Thanx again Fellas


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