Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Jan Wed 22, 2020 11:19 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 5 posts ] 
Author Message
 Post subject: Voice of Music 1275 recap, now tone control doesn't work
PostPosted: Sep Wed 04, 2019 1:18 am 
New Member

Joined: Sep Wed 04, 2019 1:15 am
Posts: 3
Hello,

I recently recapped a VM 1275 record player. The tone control was working before, but now it does nothing. I have tried resoldering the connections, and changed out the capacitors to make sure they were good. Can anyone help? I am looking for other things to check. I also took the pot apart, and cleaned that as well.

Jerrod


Top
 Profile  
 
 Post subject: Re: Voice of Music 1275 recap, now tone control doesn't work
PostPosted: Sep Wed 04, 2019 8:04 am 
Member
User avatar

Joined: Sep Mon 16, 2013 2:42 am
Posts: 3621
Location: Tucson, Arizona U.S.A.
If it used to work and now it doesn't, there are a few possibilities. The most likely is that something got connected wrong. Then it is possible that a wrong value part was installed. The chance of a bad part is very low if they were all fresh, new parts, but you already changed them to eliminate the possibility (it is still possible for an entire production run to be bad, or damaged somehow,, but that is really, really unlikely).

I would go over the schematic with a highlighter or colored pencil making sure everything was wired right and is the right value.

_________________
Jim Mueller


Top
 Profile  
 
 Post subject: Re: Voice of Music 1275 recap, now tone control doesn't work
PostPosted: Sep Wed 04, 2019 12:07 pm 
Member
User avatar

Joined: Jul Mon 26, 2010 8:30 pm
Posts: 27091
Location: Annapolis, MD
Simple circuit---easy to check for miswires.

My best guess is that there was a decimal point slip when picking the replacement for C5.

BUT---note that the tone control goes to chassis ground and not B-. Thus, if C7 is the wrong value or missing......

I'm looking at the schematic found here:
https://www.radiomuseum.org/r/vm_1275.html

_________________
-Mark
"Measure voltage, but THINK current." --anon.


Top
 Profile  
 
 Post subject: Re: Voice of Music 1275 recap, now tone control doesn't work
PostPosted: Sep Wed 04, 2019 4:36 pm 
New Member

Joined: Sep Wed 04, 2019 1:15 am
Posts: 3
Thanks for all the info. I replaced C5 with a 332/630 volt capacitor. I thought that might be wrong do I also tried a 302k/630 one I had. The schematic says C5 is .0033, but the one I pulled out looks like it says .003.

I’m not that good at converting, if you can help. Neither one of these values fixed it. And I am pretty sure I wired everything correctly. I know it will be hard to tell, but I will attach before and after pics.


Top
 Profile  
 
 Post subject: Re: Voice of Music 1275 recap, now tone control doesn't work
PostPosted: Sep Wed 04, 2019 6:10 pm 
Member
User avatar

Joined: Jul Mon 26, 2010 8:30 pm
Posts: 27091
Location: Annapolis, MD
0.003000uF = 3nF (nanofarad) = 3000pF (picofarad)

The quasi-scientific notation is 302, meaning 30 and 2 zeros or 30 X 10^2. True scientific notation would be 3E3,which reads as 3 X 10^3.

All that aside, you can use 302 or 332 there and never hear the difference.

How about the grounding question?

Also, put an ohmmeter from the pot wiper to the ground end, and verify the resistance changes smoothly throughout the rotation.

_________________
-Mark
"Measure voltage, but THINK current." --anon.


Top
 Profile  
 
Post New Topic Post Reply  [ 5 posts ]  Moderator: Alan Voorhees

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 15 guests



Search for:
Jump to:  


























-->


Privacy Policy :: Powered by phpBB