ANTIQUE-RADIO-LAB
Welcome, please log-in to participate in this (your) forum, by logging in you agree to abide by the rules of this forum. Until you make your FIRST post you cannot PM a Member.
ANTIQUE-RADIO-LAB

Antique Radio Forum for Collectors antique-radio-lab.forumotion.com
 
HomeHome  RegisterRegister  Log inLog in  FAQFAQ  PublicationsPublications  SearchSearch  
Need Help Logging In?: 1st. thing is to clean out your cookies. if that doesn't work then Down at the bottom of the page, there is a Contact field that you can click on.
Any other usage, ( other than registration or Login Help) will be ignored. For other questions go to our FAQs link above.

Share | 
 

 Magnavox 1-ST-621

Go down 
AuthorMessage
19&41
Senior Member 75+ Posts
Senior Member 75+ Posts
avatar

Join date : 2014-08-19

PostSubject: Magnavox 1-ST-621    December 1st 2017, 11:21 am

I've just brought my next project home.  A Magnavox stereo console.  I've harvested much of the soil deposited in the cabinet and have pulled the amplifier chassis to start the process.  the cabinet has one problem.  It appears that there has been stain spilled on the sliding covers on top.  Any ideas on how to attempt to remove it?

_________________
"Any sufficiently advanced technology is indistinguishable from magic."
— Arthur C. Clarke
Back to top Go down
FrankB
Moderator
Moderator
avatar

Join date : 2010-11-22

PostSubject: Re: Magnavox 1-ST-621    December 14th 2017, 5:42 pm

About all I can offer is to sand off the finish and re-stain and shoot it with lacquer. That was a very thin veneer or printed plastic overlay, I think. I never did any cabinet repair back then, except some scratch cover up.
your best bet is to find another console with a good set of sliding lids. They should be cheap, in the 10-15 buck range. 

 On the radio: If its solid state replace ANY electrolytic in it with the black paper covering. Even back in the late 70's those were failing like mad. Made good bux replacing them.

 OTT, IIRC that there was a zener in the FM tuning section that failed, and one FM (osc?) transistor that, IMIC, is replaceable by an ECG 222. The original had a 4th lead, but it was just a shield, I think.

 That design seldom had any other problems, except being a PITA to get the chassis out.

(Geez- that's like remembering back almost 40 years!)

Then comes the complete go thru of that Collero T/T LOL Actually fairly simple to rebuild or repair.
Mostly gummed up lube and sticky motors. Another fairly EZ repair and was a high profit for me way back when.
Back to top Go down
Cliff Jones
Site Administrator
Site Administrator
avatar

Join date : 2010-11-22

PostSubject: Re: Magnavox 1-ST-621    December 15th 2017, 1:59 pm

what kind of stain? paint? water? Ink?

_________________
I'm a Science Thinker, Radio Tinkerer, and all around good guy. Just ask Me!
Back to top Go down
FrankB
Moderator
Moderator
avatar

Join date : 2010-11-22

PostSubject: Re: Magnavox 1-ST-621    December 15th 2017, 8:08 pm

A lacquer stain.

My friend who was a cabinet maker, and wrote books and taught it, told me that the cabinets had been tinted/toned/colored by a nitrocellulose lacquer based stain.

 He hated using it, as it gave him massive headaches due to a chemical sensitivity, even with a chemical respirator .

Maybe this type of lacquer is why the cabinets burned so well, as nitrocellulose is extremely flammable. 
(Also why that type of film is hazardous to store & use, and was made illegal in theaters as it caused many fires.)
Back to top Go down
19&41
Senior Member 75+ Posts
Senior Member 75+ Posts
avatar

Join date : 2014-08-19

PostSubject: Re: Magnavox 1-ST-621    January 28th 2018, 8:18 am

I went ahead and removed What was left of the original finish from the sliders, and applied some laundry bleach to the darkened areas and rinsed it off and repeated once again.  after everything was dry it was slightly lighter.  I got some pigmented oil finish and gave it two applications and now they are a bit dark, but pretty even.  I have recapped the amplifier demultiplexer and tuner, as well as the crossover caps.  reassembled everything and no audio.  Went back through and found the tuners' dual audio amplifier tube to have an open filament.  Awaiting a replacement.

_________________
"Any sufficiently advanced technology is indistinguishable from magic."
— Arthur C. Clarke
Back to top Go down
19&41
Senior Member 75+ Posts
Senior Member 75+ Posts
avatar

Join date : 2014-08-19

PostSubject: Re: Magnavox 1-ST-621    March 12th 2018, 1:05 pm

Also found one of the 4 final output push pull tubes were bad.  The tuner gave me fits trying to work out what the problem was as I was getting no output from it.  It had continually variable voltages at the 6EU7 output amplifier tube after replacing it with a known good tube.  As test socket extenders are  ridiculously pricy, I had to take the voltage measurements from the socket tabs.  While I was going through it the radio audio started coming through weakly.  A friend suggested trying it with no shield on  the tube.  It then came through a little stronger.  I moved the tube slightly in it's socket and the unit began blaring at full volume.  I shut it down.  It had a socket that used flat contacts on each side of the pins.  I closed each with my hemostats and it came to life.  It sounds better than I had hoped for.  The turntable will take a while longer, so I am using my laptop music library with it.


_________________
"Any sufficiently advanced technology is indistinguishable from magic."
— Arthur C. Clarke
Back to top Go down
19&41
Senior Member 75+ Posts
Senior Member 75+ Posts
avatar

Join date : 2014-08-19

PostSubject: Re: Magnavox 1-ST-621    March 19th 2018, 5:52 am

The console's FM receiver has drifted far off in frequency, so much so, it lost about 1/3 of it's bandspread. The alignments covered in it's photofact had very little effect on it.  I set about trying another receiver I had purchased earlier, to see if it would come closer to working correctly.  It was 2 years older and the dial glass was inverted from my unit's orientation and the indicator meter was as well.  I replaced the glass with the original,  And I pulled and rotated the meter.  After recapping and cleaning it out, I connected it and turned on the unit.  No lights,nor power.  So I had to go through and clean and restress all the Molex interconnects That carries the trunked power.  Tried it again and it came on, sounding nice with the FM while still off the indicated frequency, covering its whole bandspread.  The alignments specified in the photofact results in a miniscule change in the center frequency, So I guess I'll have to live with it.

_________________
"Any sufficiently advanced technology is indistinguishable from magic."
— Arthur C. Clarke
Back to top Go down
Cliff Jones
Site Administrator
Site Administrator
avatar

Join date : 2010-11-22

PostSubject: Re: Magnavox 1-ST-621    March 19th 2018, 10:43 am

Some circuits are so critical even replacing a component with a replacement that doesn't have exactly the same lead length or even the posistion can effect performance. A missing tube sheild or wrong brand of tube can cause a person to want to tear thier hair out ( even if they have little hair left LOL ). As components age also they can effect drift. Even though they measure correctly. See if there are any temperature compensating resistors. 

Nice to see you didn't give up on an alternative solution though.

_________________
I'm a Science Thinker, Radio Tinkerer, and all around good guy. Just ask Me!
Back to top Go down
19&41
Senior Member 75+ Posts
Senior Member 75+ Posts
avatar

Join date : 2014-08-19

PostSubject: Re: Magnavox 1-ST-621    March 19th 2018, 12:43 pm

With one in operation, I'm going to check all the possible variables I can access in the RF/IF and the ratio detector on the other.  Maybe I can end up with 2 good ones.

_________________
"Any sufficiently advanced technology is indistinguishable from magic."
— Arthur C. Clarke
Back to top Go down
19&41
Senior Member 75+ Posts
Senior Member 75+ Posts
avatar

Join date : 2014-08-19

PostSubject: Re: Magnavox 1-ST-621    April 9th 2018, 1:59 pm

Seeing folks get new goodies for the spring, I thought I would get a PC based oscilloscope interface to so some troubleshooting in the receiver.  I also got a set of ceramic alignment screwdrivers  They are doing nicely after getting the slugs freed up with a metallic tool.

_________________
"Any sufficiently advanced technology is indistinguishable from magic."
— Arthur C. Clarke
Back to top Go down
Cliff Jones
Site Administrator
Site Administrator
avatar

Join date : 2010-11-22

PostSubject: Re: Magnavox 1-ST-621    April 9th 2018, 3:24 pm

Where did you get the ceramic screwdrivers?
Cost?

_________________
I'm a Science Thinker, Radio Tinkerer, and all around good guy. Just ask Me!
Back to top Go down
19&41
Senior Member 75+ Posts
Senior Member 75+ Posts
avatar

Join date : 2014-08-19

PostSubject: Re: Magnavox 1-ST-621    April 9th 2018, 4:02 pm

I got mine on Ebay, but this amazon source ought to be available for longer.  It is about the same price.  they come in various flats and phillips and the shafts are hex.

https://www.amazon.com/Anti-static-Ceramic-Adjust-Frequency-Screwdriver/dp/B01LLA5H14/ref=sr_1_3_a_it?ie=UTF8&qid=1523314787&sr=8-3&keywords=ceramic+screwdriver

_________________
"Any sufficiently advanced technology is indistinguishable from magic."
— Arthur C. Clarke
Back to top Go down
19&41
Senior Member 75+ Posts
Senior Member 75+ Posts
avatar

Join date : 2014-08-19

PostSubject: Re: Magnavox 1-ST-621    April 9th 2018, 4:05 pm

One other thing that is handy to have with these are diamond burs for your rotary tool.  It makes it easy to reform a broken flat tip.

_________________
"Any sufficiently advanced technology is indistinguishable from magic."
— Arthur C. Clarke
Back to top Go down
Cliff Jones
Site Administrator
Site Administrator
avatar

Join date : 2010-11-22

PostSubject: Re: Magnavox 1-ST-621    April 9th 2018, 4:38 pm

Ordered meself says I.

_________________
I'm a Science Thinker, Radio Tinkerer, and all around good guy. Just ask Me!
Back to top Go down
19&41
Senior Member 75+ Posts
Senior Member 75+ Posts
avatar

Join date : 2014-08-19

PostSubject: Re: Magnavox 1-ST-621    April 9th 2018, 5:00 pm

They seem to do better than plastics for the flat tip purposes.  I have yet to see a phillips slug. Smile

_________________
"Any sufficiently advanced technology is indistinguishable from magic."
— Arthur C. Clarke
Back to top Go down
FrankB
Moderator
Moderator
avatar

Join date : 2010-11-22

PostSubject: Re: Magnavox 1-ST-621    April 9th 2018, 5:37 pm

Motorola issued them to their authorized repair shops too.
Back to top Go down
19&41
Senior Member 75+ Posts
Senior Member 75+ Posts
avatar

Join date : 2014-08-19

PostSubject: Re: Magnavox 1-ST-621    April 9th 2018, 6:53 pm

That's where I first got them.

_________________
"Any sufficiently advanced technology is indistinguishable from magic."
— Arthur C. Clarke
Back to top Go down
Sponsored content




PostSubject: Re: Magnavox 1-ST-621    

Back to top Go down
 
Magnavox 1-ST-621
Back to top 
Page 1 of 1

Permissions in this forum:You cannot reply to topics in this forum
ANTIQUE-RADIO-LAB :: Radio Repair Bench :: Radios -Tube type-
Jump to: