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 Post subject: RCA 6T Schematic
PostPosted: Nov Fri 24, 2017 5:01 pm 
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Joined: Jan Mon 11, 2016 1:19 pm
Posts: 280
Location: Spring Lake Mi
Hi guys, I'm restoring this radio but need a schematic I can read, I have (Rider)it is very hard to read. I have the radio up and running but do have a volume issue, the radio has to be at max the hear anything. I still need to check voltages and resistors. One question, there is a Cap of .035 1000v (C26) from tone control to pin 3 of the 6F6, I used a .047 1k is that okay.
All caps have been replaced.

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Jim KA8ZXJ
Spring Lake MI 49456


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 Post subject: Re: RCA 6T Schematic
PostPosted: Nov Fri 24, 2017 5:35 pm 
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Location: Mountains of Mourne. Ireland.
RCA 7-37 http://americanradiohistory.com/hd2/IDX ... e-0222.pdf
RCA 7-38 http://americanradiohistory.com/hd2/IDX ... e-0223.pdf
RCA 7-39 http://americanradiohistory.com/hd2/IDX ... e-0224.pdf
RCA 7-40 http://americanradiohistory.com/hd2/IDX ... e-0225.pdf

Greg.


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 Post subject: Re: RCA 6T Schematic
PostPosted: Nov Fri 24, 2017 5:48 pm 
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Location: Livermore, CA
Jim

A slightly larger cap for C26 will decrease high frequency response a little more at end of tone adjustment. .047 mf will work.

One end of the cap is connected to plate of the output tube (B+). The other end to tone control and ground. If the original cap becomes leaky it will damage the tone control.

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 Post subject: Re: RCA 6T Schematic
PostPosted: Nov Fri 24, 2017 8:02 pm 
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Joined: Jan Mon 11, 2016 1:19 pm
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Location: Spring Lake Mi
egg wrote:

Thank you Greg it is a lot clearer than the copy I have..................

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Jim KA8ZXJ
Spring Lake MI 49456


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 Post subject: Re: RCA 6T Schematic
PostPosted: Nov Fri 24, 2017 8:05 pm 
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Joined: Jan Mon 11, 2016 1:19 pm
Posts: 280
Location: Spring Lake Mi
Norm Leal wrote:
Jim

A slightly larger cap for C26 will decrease high frequency response a little more at end of tone adjustment. .047 mf will work.

One end of the cap is connected to plate of the output tube (B+). The other end to tone control and ground. If the original cap becomes leaky it will damage the tone control.

Thanks Norm, Have found several (dog bone) resistors out of tolerance we'll see what transpires.

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Jim KA8ZXJ
Spring Lake MI 49456


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 Post subject: Re: RCA 6T Schematic
PostPosted: Nov Sun 26, 2017 1:59 am 
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Joined: Jan Mon 11, 2016 1:19 pm
Posts: 280
Location: Spring Lake Mi
Hay guy's, I need to get a new volume control for this radio. This is a new venture for me, how do I identify it. In one of the reply's are the schematics the first one is the one that shows the volume control. It is a volume control only but it has an extra tap four of them. The single tap shows 600K to chassis gnd. the two top taps show 400K, also I see 2 MEG. total. Oldradioparts.com has quite a list of them, I don't have a clue what to look for.
I would ask in classifieds but don't know what to ask for!!!!!!!!
HELP...........thanks.

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Jim KA8ZXJ
Spring Lake MI 49456


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 Post subject: Re: RCA 6T Schematic
PostPosted: Nov Mon 27, 2017 1:13 am 
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Joined: Jan Mon 11, 2016 1:19 pm
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Location: Spring Lake Mi
Put an WTB ad in the classifieds.

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Jim KA8ZXJ
Spring Lake MI 49456


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 Post subject: Re: RCA 6T Schematic
PostPosted: Nov Mon 27, 2017 6:25 pm 
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Joined: Jan Mon 11, 2016 1:19 pm
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Location: Spring Lake Mi
Me bad................found that the 6H6 was bad...........don't ask!

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Jim KA8ZXJ
Spring Lake MI 49456


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 Post subject: Re: RCA 6T Schematic
PostPosted: Nov Wed 29, 2017 10:24 pm 
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Joined: Jan Mon 11, 2016 1:19 pm
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Location: Spring Lake Mi
Still having an issue's....The volume control is strange, with the volume all the way down hear nothing, turn it just a fraction the station come in, turn it another fraction towards high the station cuts out, until I get to 2/3 of the control the station comes in and the control act's normal on the last third of the control, the volume goes from low to high.
Also when I touch the grid of the 6A8 with a screw driver I do not get a hum, I can hear that I am touching it a clicking noise and the station signal is diminished some. When I touch the center post of the volume control which is the grid of the 6F5 audio tube same thing happens. But with the volume control at max it is really loud.
Do you think this is a volume control issue or something more. I have recapped and changed most all of the resistors, and changed out most of the tubes with ones that tested better.
All the voltage checked good according to the schematic.

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Jim KA8ZXJ
Spring Lake MI 49456


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 Post subject: Re: RCA 6T Schematic
PostPosted: Nov Thu 30, 2017 3:45 am 
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Jimradio wrote:
Still having an issue's....The volume control is strange, with the volume all the way down hear nothing, turn it just a fraction the station come in, turn it another fraction towards high the station cuts out, until I get to 2/3 of the control the station comes in and the control act's normal on the last third of the control, the volume goes from low to high.

I'm guessing that this area of the VC would have been where the normal loudness range was set to, and as such, the carbon track in that range eventually became worn out. I'd replace the VC, if for nothing else than to rule it out as a troublemaker.

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 Post subject: Re: RCA 6T Schematic
PostPosted: Nov Thu 30, 2017 1:15 pm 
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Joined: Jan Mon 11, 2016 1:19 pm
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Location: Spring Lake Mi
fifties wrote:
Jimradio wrote:
Still having an issue's....The volume control is strange, with the volume all the way down hear nothing, turn it just a fraction the station come in, turn it another fraction towards high the station cuts out, until I get to 2/3 of the control the station comes in and the control act's normal on the last third of the control, the volume goes from low to high.

I'm guessing that this area of the VC would have been where the normal loudness range was set to, and as such, the carbon track in that range eventually became worn out. I'd replace the VC, if for nothing else than to rule it out as a troublemaker.

Thank you for that advice, needed to hear it from someone else. Love this forum.

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Jim KA8ZXJ
Spring Lake MI 49456


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 Post subject: Re: RCA 6T Schematic
PostPosted: Dec Tue 05, 2017 2:04 pm 
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Joined: Jan Mon 11, 2016 1:19 pm
Posts: 280
Location: Spring Lake Mi
Guy's,
Finely got it working. Can not say what fixed it, new volume control, re-soldered cap's on the 6A8 & 6F5 helped some, replaced the 6F6 output tube. The last thing I did was to clean the new volume control with Deoxit, that made a great improvement. Having so many things that needed cleaning, replacement, alignment etc.
I guess that is why we do this, I'm getting balder.

Thanks to all of you on this forum.

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Jim KA8ZXJ
Spring Lake MI 49456


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 Post subject: Re: RCA 6T Schematic
PostPosted: Dec Tue 05, 2017 5:25 pm 
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Joined: Jan Mon 11, 2016 1:19 pm
Posts: 280
Location: Spring Lake Mi
Attachment:
DSC07003.JPG
DSC07003.JPG [ 154.71 KiB | Viewed 146 times ]

This is what it looks like ...........

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Jim KA8ZXJ
Spring Lake MI 49456


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