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 Post subject: Condenser/capacitor block replacement
PostPosted: Jan Wed 17, 2018 9:04 pm 
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I have recently received a Gulbransen model 60 chassis. I believe one of the 24A tubes have been exposed to air. When starting the radio the tubes glow besides the aired one and I get a faint signal from stations. volume control does not work. After 10 minutes of running I believe the condenser block smoked for a few seconds and stopped but had no effect. I will be ordering the new tube soon and I would like to replace the condenser block. I have some understanding on how to replace a cap but not a whole block. Some information on how to proceed will be Great! I am still new to this. I have posted this on other forums with no response.


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 Post subject: Re: Condenser/capacitor block replacement
PostPosted: Jan Wed 17, 2018 11:34 pm 
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If you know how to read a schematic that's the easiest way to figure things out. If its an electrolytic capacitor then look for the values and the polarity on the cardboard box. Sometimes they will share a common negative lead. You can usually just cut the whole thing out, install modern caps in its place. Don't run the set until you at least replace the electrolytics since the one in there now is probably shorted and that can ruin the power transformer.


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 Post subject: Re: Condenser/capacitor block replacement
PostPosted: Jan Wed 17, 2018 11:39 pm 
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I have the schematic here: https://www.radiomuseum.org/r/gulbransen_60.html. When replacing this huge block I am confused where all the separate caps ground would go and what voltage to use. Thanks!


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 Post subject: Re: Condenser/capacitor block replacement
PostPosted: Jan Wed 17, 2018 11:43 pm 
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Joined: Jul Sun 26, 2015 11:34 pm
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Location: Hurdle Mills, North Carolina
Here is the schematic with the condenser block information on what is in it. http://www.nostalgiaair.org/pagesbymode ... 040033.pdf The hardest part may be getting the old capacitors removed, blocks are usually tar filled. I have had success with freezing the blocks, drilling out the contents, but most of the time I heat the block with a butane torch.
You should plan on replacing all of the capacitors in the block with the values stated and 630vdc rated capacitors.

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 Post subject: Re: Condenser/capacitor block replacement
PostPosted: Jan Wed 17, 2018 11:47 pm 
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Location: Hurdle Mills, North Carolina
All of the capacitors except for the capacitor labeled H have one side tied to the chassis for ground.

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Larry in NC


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 Post subject: Re: Condenser/capacitor block replacement
PostPosted: Jan Wed 17, 2018 11:56 pm 
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For the caps should I stick at 630v for all of them in the block?


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 Post subject: Re: Condenser/capacitor block replacement
PostPosted: Jan Thu 18, 2018 12:44 am 
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Location: Hurdle Mills, North Carolina
Yes if it were mine that is what I would do.

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 Post subject: Re: Condenser/capacitor block replacement
PostPosted: Jan Thu 18, 2018 1:12 am 
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Thanks! I will update when I order the caps and replace them.


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 Post subject: Re: Condenser/capacitor block replacement
PostPosted: Jan Thu 18, 2018 2:00 am 
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Location: Mountains of Mourne. Ireland.
Here are the original Voltages as shown on the schematic. Gulbransen page 1-1
Image
C17 is on the primary side of the power transformer.

Greg.


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 Post subject: Re: Condenser/capacitor block replacement
PostPosted: Jan Thu 18, 2018 4:25 am 
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If I do not wire c-17 H to chassis ground how would I wire it? would I only use one cap or two?


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 Post subject: Re: Condenser/capacitor block replacement
PostPosted: Jan Thu 18, 2018 6:39 am 
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Location: Mountains of Mourne. Ireland.
The connection points for C17 can be seen in the chassis wiring diagram, highlighted here. Gulbransen page 1-2
Image
The X shown on the primary side of the power transformer is the A.C. switch.

C17 is not marked on the schematic.
Use only one capacitor (for C17). All leads insulated.

Greg.


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 Post subject: Re: Condenser/capacitor block replacement
PostPosted: Jan Thu 18, 2018 12:28 pm 
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Location: Annapolis, MD
C17 (AKA H-H) is tied to one side of the the AC line. This should by a type Y2 "safety cap".

I advocate always restuffing these capacitor boxes....it is the only way to preserve the lead dress, which could be the secret to avoiding oscillation or stability problems.

I would, however, make c17 separate, grounded to the chassis for the shortest possible lead length.

Regardless of the type of caps used, I don't like the idea of line voltage going into one of those potted modules.

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-Mark http://pixellany.com

"It's always something". --Gilda Radner (1946 - 1989)


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 Post subject: Re: Condenser/capacitor block replacement
PostPosted: Jan Thu 18, 2018 7:50 pm 
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Okay what I plan on doing after seeing this is to replace the caps with the shortest wire possible. I will ground all the caps to the block except for c-17, it will be grounded right to the chassis. Just checking before I move forward.


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 Post subject: Re: Condenser/capacitor block replacement
PostPosted: Jan Thu 18, 2018 8:03 pm 
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Joined: Jan Wed 17, 2018 8:59 pm
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I do not want to mess this up and sorry for asking so many questions, but where should I buy these caps and what similar values could I use because most of these values appear to be not used anymore. Thanks!


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 Post subject: Re: Condenser/capacitor block replacement
PostPosted: Jan Thu 18, 2018 9:13 pm 
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Location: Carrollton Georgia
I just got done stuffing my block on my philco 625. I just took a screw driver and poped the tar seal out and it crumbled. Cleaned up real nice. If i cant find the exact value of cap i will put some in paraell tl get the value i want. For example i needed a .3 uf . I put three .1uf caps to make the .3 i needed. Or it you have a value close it should work. Like my schematic call for a .9uf. I used a .11.

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 Post subject: Re: Condenser/capacitor block replacement
PostPosted: Jan Thu 18, 2018 10:30 pm 
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Joined: Jan Wed 17, 2018 8:59 pm
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https://www.tubesandmore.com/products/c ... dial-leads

I plan on using this cap to replace them all using there respected values. Just checking if this would Work.


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 Post subject: Re: Condenser/capacitor block replacement
PostPosted: Jan Fri 19, 2018 12:21 am 
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Yes those should work fine. 630 volt is good

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 Post subject: Re: Condenser/capacitor block replacement
PostPosted: Jan Fri 19, 2018 2:34 am 
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Joined: Jan Wed 17, 2018 8:59 pm
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Okay I plan on replacing the caps with the shortest wire possible. I will ground all the caps to the block except for c-17, it will be grounded right to the chassis. Total of 16 caps. double checking before I buy these caps.


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 Post subject: Re: Condenser/capacitor block replacement
PostPosted: Jan Fri 19, 2018 2:38 am 
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Location: Annapolis, MD
I still argue for using a "safety cap" for C17, and NOT putting it in the can.,,,,see my earlier post.

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-Mark http://pixellany.com

"It's always something". --Gilda Radner (1946 - 1989)


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 Post subject: Re: Condenser/capacitor block replacement
PostPosted: Jan Fri 19, 2018 3:10 am 
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Joined: Jan Tue 31, 2012 1:55 am
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Location: Mountains of Mourne. Ireland.
To the Rescue - The Advent of Safety Capacitors.
"If tube radios were manufactured today in 2018, AC rated line filter safety capacitors would be required".
David Cantelon, JustRadios.

http://www.justradios.com/safetytips.html

Greg.


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