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


It is currently Jan Wed 20, 2021 1:20 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 23 posts ]  Go to page 1, 2  Next
Author Message
 Post subject: Automatic radio model CL -152M silver mica disease
PostPosted: Jun Wed 05, 2019 1:43 pm 
Member

Joined: May Tue 31, 2016 9:49 pm
Posts: 342
Location: Mineral Wells, tx 76067
Gentlemen,
I recently acquired an Automatic radio mfd. about 1954 that has silver mica disease. I would like to attempt to repair the 1st and 2nd I.F. transformers by removing the internal capacitors and by installing external capacitors in the circuit. The schematic does not show the values of the internal capacitors . Does anyone have any idea of what the values might be? These are 3/4 by 3/4 inch units and if all else fails where can I obtain to replacement units? thanks
Walt


Top
 Profile  
 
 Post subject: Re: Automatic radio model CL -152M silver mica disease
PostPosted: Jun Wed 05, 2019 2:05 pm 
Member

Joined: Nov Tue 14, 2017 5:09 am
Posts: 3275
Location: Austin, Texas
Walt,
Howdy from Austin.
Here is my procedure for replacing the caps:
https://drive.google.com/file/d/1mvs5qBTzb-HV8eujm_kallH9JvRO8DKt/view?usp=sharing
The caps will most likely be in the 75pF to 120pF range.
I recommend that you get one of the low cost capacitance meters like this one to measure the caps in the transformers you are repairing:
https://www.ebay.com/itm/ELIKE-DT6013-Capacitance-Meter-Capacitor-Tester-0-1pF-to-20mF-with-Data-Hold/273860969811
Probably any of the meters with a 200pF range will work but I have the one above and it has been very accurate.
Edit: I noticed that the first picture on the link above is not correct. The second picture is the DT-6013.

Jay


Top
 Profile  
 
 Post subject: Re: Automatic radio model CL -152M silver mica disease
PostPosted: Jun Wed 05, 2019 4:45 pm 
Member

Joined: May Tue 31, 2016 9:49 pm
Posts: 342
Location: Mineral Wells, tx 76067
Thanks Jay,
I will review the info you sent me and see what I can come up with . I'll let you know if I am successful.
walt


Top
 Profile  
 
 Post subject: Re: Automatic radio model CL -152M silver mica disease
PostPosted: Jun Wed 05, 2019 8:55 pm 
Member
User avatar

Joined: Jan Tue 31, 2012 1:55 am
Posts: 15327
Location: Mountains of Mourne. Ireland.
Walt, here's a neat video.

Watch: Replacing mica capacitors in an AA5 I.F. transformer.
http://antiqueradios.com/forums/viewtop ... 6#p2765766
Listen to... Part one. Introduction. Silver Mica Disease.

The capacitance is achieved by using thin sheets/wafers of Mica.

also... here is the late Paul Pinyot's take on the matter.
IF Transformer Repair.
https://www.radiomuseum.org/forum/if_tr ... epair.html

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

Here is an unorthodox method of figuring-out the required Capacitances.

Determining I.F. transformer capacitance values with temporary V-caps tuned for maximum static/noise!

Watch: Edited 4min clip: https://www.youtube.com/embed/jQb4lPNcB ... autoplay=0
Complete video: https://www.youtube.com/watch?v=jQb4lPNcBMc


google→ how to save youtube videos... :)
:) Greg.

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

Watch: Two excellent alignment procedure videos (not found with a google or youtube search).
http://antiqueradios.com/forums/viewtop ... 1#p2645421


Top
 Profile  
 
 Post subject: Re: Automatic radio model CL -152M silver mica disease
PostPosted: Jun Wed 05, 2019 9:14 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 1254
Location: Earth
Most likely it uses transformers that have a 131 pF and 106 pF cap in each.

These were very common values during this era of radio.


Top
 Profile  
 
 Post subject: Re: Automatic radio model CL -152M silver mica disease
PostPosted: Jun Wed 05, 2019 10:14 pm 
Member

Joined: May Tue 31, 2016 9:49 pm
Posts: 342
Location: Mineral Wells, tx 76067
Dr . Radio
Those values are very similar. Does it matter which goes where? And its been a while since I ordered this type of capacitor and I cannot think of the company I used to order from. Please suggest some names. I want to thank everyone for their valuable suggestions to help me out.
walt


Top
 Profile  
 
 Post subject: Re: Automatic radio model CL -152M silver mica disease
PostPosted: Jun Thu 06, 2019 12:28 am 
Member

Joined: Nov Tue 14, 2017 5:09 am
Posts: 3275
Location: Austin, Texas
Just Radios (ad on right of this page) has silver mica caps. You will need two caps to get the exact values like a 100pF and a 6pF to get 106pF.
https://www.justradios.com/cart.html

You do want to get the correct value on each side. Be sure to mark the mica before you remove it as directed in my repair procedure. You will be able to tell if the caps are different values by their size on the mica. However, there are a lot of different values used in the transformers so it's best to measure the originals. Some Miller replacements:
Attachment:
Miller1.jpg
Miller1.jpg [ 81.08 KiB | Viewed 1396 times ]

Attachment:
Miller2.jpg
Miller2.jpg [ 77.14 KiB | Viewed 1396 times ]

Jay


Top
 Profile  
 
 Post subject: Re: Automatic radio model CL -152M silver mica disease
PostPosted: Jun Thu 06, 2019 12:56 am 
Member
User avatar

Joined: Jan Tue 31, 2012 1:55 am
Posts: 15327
Location: Mountains of Mourne. Ireland.
Jay is a member at radiomuseum.org
maybe he could look at the Photofact for your I. F. Transformer capacitor values - sometimes it is noted.

Automatic Models CL-152B CL-152M CL-164B
12BE6 12BA6 12AT6 50C5 35W4

Sams Photofact Set-192 Folder-3 can be downloaded from radiomuseum.org for free.
https://www.radiomuseum.org/r/automatic_cl164b.html
Click a schematic page from the right-hand scrolling window, then again in the main center window.
The bottom four pages are Sams, the top one is from Riders.
Each page will be emailed to you immediately.
You can only download three pages a day + up to a maximum of ten every 30 days.

If you experience any downloading difficulties... see this→ viewtopic.php?p=2571007#p2570117
pdf attachments are not visible in junk email folders.

Greg.


Top
 Profile  
 
 Post subject: Re: Automatic radio model CL -152M silver mica disease
PostPosted: Jun Thu 06, 2019 1:06 am 
Member

Joined: Nov Tue 14, 2017 5:09 am
Posts: 3275
Location: Austin, Texas
Sams lists replacement IF transformers but no cap values. The replacement for the input is Merit BC-352 and the output is BC-353. Since there are two part numbers, they probably have different capacitor values.

Jay


Top
 Profile  
 
 Post subject: Re: Automatic radio model CL -152M silver mica disease
PostPosted: Jun Thu 06, 2019 2:22 am 
Member
User avatar

Joined: Jan Tue 31, 2012 1:55 am
Posts: 15327
Location: Mountains of Mourne. Ireland.
Merit BC-352 crosses to Miller 12-C1 • 455 KC Midget input I.F. trans.
Merit BC-353 crosses to Miller 12-C2 • 455 KC Midget interstage I.F. trans.

The last post in this thread suggests 150pF (picofarad).
viewtopic.php?f=6&t=230315

and these tested (prior to removal) at 100pF
viewtopic.php?f=6&t=237528

Greg.


Top
 Profile  
 
 Post subject: Re: Automatic radio model CL -152M silver mica disease
PostPosted: Jun Fri 07, 2019 1:42 am 
Member

Joined: May Tue 31, 2016 9:49 pm
Posts: 342
Location: Mineral Wells, tx 76067
I was able to complete the first transformer operation, but have not tackled the second one yet . It is a very tedious operation and the hardest part was just getting the wires off the transformer contacts. I did not note the exact position of the mica wafer before I removed it but I did notice that it has different size little white sections so I guess that indicates that they are different values . Fortunately both transformers are of the same part number ( 1655-16) so when I disassemble the second one I can note the positions relative to the green dot.
So how do I actually measure the capacitance? Just put the probes across each white section ? Thanks again for all the help.
walt


Top
 Profile  
 
 Post subject: Re: Automatic radio model CL -152M silver mica disease
PostPosted: Jun Fri 07, 2019 2:33 am 
Member

Joined: Nov Tue 14, 2017 5:09 am
Posts: 3275
Location: Austin, Texas
Measuring small caps requires some care to eliminate errors. I usually hold the mica sheet vertical with some medical forceps clamped on a clear area. You can hold a probe touching one side of the cap with your hand. The other probe needs to be held with something like a plastic or wooden stick a few inches long to keep your hand from changing the capacitance reading. I bring the second probe up close to the mica and set the meter to zero or note the value it reads just before contacting the silver on the mica. After you get the capacitance reading, you have to subtract the stray capacitance reading if it wasn't zero before the probe touched the silver.

If the transformers were making noise, there is probably a path between the two capacitors that is visible on the mica. The measured values will be more accurate if that path is scraped away before making the measurement. You can also just cut the two caps apart.

Jay


Top
 Profile  
 
 Post subject: Re: Automatic radio model CL -152M silver mica disease
PostPosted: Jun Sat 08, 2019 1:40 pm 
Member

Joined: May Tue 31, 2016 9:49 pm
Posts: 342
Location: Mineral Wells, tx 76067
Good morning guys,
Everyone has contributed a lot of good ideas and references to help me out with my capacitor problem. So at this point it seems that I have two options: purchase a digital capacitance meter and take my best reading from the mica wafer or just make an educated guess and do some trial and error tests to see what happens.

But , I was just wondering if there might be a cross reference source that I could use to determine the cap values in the I.F transformers in this radio . They both have the same part number ( 1655-16 ) and it seems I should be able to tie that in with some manufacturer if I had the source material . If this is not possible please excuse my ignorance and give me a good verbal tongue thrashing in your next reply. thanks
walt


Top
 Profile  
 
 Post subject: Re: Automatic radio model CL -152M silver mica disease
PostPosted: Jun Sat 08, 2019 1:48 pm 
Member

Joined: Feb Thu 28, 2019 7:48 pm
Posts: 616
Location: Lawrenceville, Illinois 62439
IF that were a 16-1655, it sounds like a Meissner part number. I don't (haven't found yet) have a catalog or cross reference, but maybe someone does and maybe it lists those values?
Dan


Top
 Profile  
 
 Post subject: Re: Automatic radio model CL -152M silver mica disease
PostPosted: Jun Sat 08, 2019 3:36 pm 
Member

Joined: Nov Tue 14, 2017 5:09 am
Posts: 3275
Location: Austin, Texas
I've measured a lot of the transformers made by Automatic Manufacturing (Code 119 on the cans). I think they may have adjusted the inductance and capacitance depending on the dielectric constant of the mica they had available. Natural mica can have a considerable variation in dielectric constant and they didn't have much choice on the size of the capacitor plates since the mica had to fit in the IF can. I am guessing that is why there is little info on the cap values. High volume users like Zenith and Philco may have specified the capacitor values but the lower volume manufacturers probably got a reduced cost by taking parts with a range of cap values.

Jay


Top
 Profile  
 
 Post subject: Re: Automatic radio model CL -152M silver mica disease
PostPosted: Jun Sat 08, 2019 3:42 pm 
Member

Joined: Nov Tue 14, 2017 5:09 am
Posts: 3275
Location: Austin, Texas
waltdavis777 wrote:
Good morning guys,
Everyone has contributed a lot of good ideas and references to help me out with my capacitor problem. So at this point it seems that I have two options: purchase a digital capacitance meter and take my best reading from the mica wafer or just make an educated guess and do some trial and error tests to see what happens.



Another option is to send one of the micas to me and I'll measure it for you. Send a PM if you want to do that.

Jay


Top
 Profile  
 
 Post subject: Re: Automatic radio model CL -152M silver mica disease
PostPosted: Jun Sat 08, 2019 4:12 pm 
Member
User avatar

Joined: Jan Tue 31, 2012 1:55 am
Posts: 15327
Location: Mountains of Mourne. Ireland.
Back in 2013 Mark/pixellany wrote:

The problem is that adding new capacitors may throw the alignment far enough off that the standard "cookbooks" no longer work.

Step 1: Hook up signal generator to the input of the last IF transformer. Set to the the lowest level** that give a usable signal, and try to peak up the transformer.

If it will peak up, then put the generator at the input of the next stage--working towards the front end--repeat the procedure.

If either (any, all) will NOT peak up, then adjust fixed capacitance as required.

Lather, rinse, repeat as required....

**lowest level is often achieved by loosely coupling the generator to the set---eg a small wire loop placed near the desired input point.
The level has to be kept low to keep the AVC circuit from fighting the alignment.
viewtopic.php?p=1928479#p1928479

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

I would begin with 100pF or 120pF capacitors.

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

For your amusement.
Tom Albrecht measured Zenith values...
https://www.antiqueradios.com/forums/vi ... 0#p2559540

Zenith I. F. Transformer values. Dan Schoo...
http://www.sparkbench.com/zenithifxfmrs.gif

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

Here is an unorthodox method of figuring-out the required Capacitances.

Determining I.F. transformer capacitance values with temporary V-caps tuned for maximum static/noise!

Watch: Edited 4min clip: https://www.youtube.com/embed/jQb4lPNcB ... autoplay=0
Complete video: https://www.youtube.com/watch?v=jQb4lPNcBMc


google→ how to save youtube videos... :)
:) Greg.


Top
 Profile  
 
 Post subject: Re: Automatic radio model CL -152M silver mica disease
PostPosted: Jun Wed 12, 2019 9:47 pm 
Member

Joined: Nov Tue 14, 2017 5:09 am
Posts: 3275
Location: Austin, Texas
I have measured the AR 1655-16 caps and they are about 91pF and 110pF. Normally the low value is on the grid side with the green dot on the terminal. I only have the mica sheets and don't know for sure on these transformers.
Here are some pictures of the caps along with some others that I have measured. You can see the silver migration paths on some of them. Some also have the values adjusted by removing part of the silver. I think they used something like a tiny sand blaster to remove the silver on one side of the cap. I have also seen some where it looked like they scraped away the silver with a knife.
Attachment:
Mica caps.jpg
Mica caps.jpg [ 121.97 KiB | Viewed 1258 times ]


I have measured enough of these to know that you can't go by the silver area to get the capacitor value. The dielectric constant of the mica varies considerably so a large area on one piece of mica may actually have less capacitance than a smaller area on a different piece even when the mica is the same thickness.

Jay


Top
 Profile  
 
 Post subject: Re: Automatic radio model CL -152M silver mica disease
PostPosted: Jun Fri 14, 2019 9:41 pm 
Member

Joined: May Tue 31, 2016 9:49 pm
Posts: 342
Location: Mineral Wells, tx 76067
Gentlemen,
Well here I am again with the results of the SMD repair:
I got the filter and other caps in the mail a few days ago and I installed them . And today Fed ex brought the 4 silver mica caps in a box way too big . I could hardly wait to unwrap and get them installed. Then I had to reconnect the clock so I could turn it on . I plugged it in and....... got a perfect sound from the radio ....no adjustments required. It was a satisfying sound that I'm sure you've all experienced. This is what it's all about for me !!!! (and probably you too).
I wish to thank all of you for your inputs and the U tube videos and especially JAY who offered to actually measure the old ones for me and recommend the correct values , which incidentally, were very close to the values some of you suggested.

What will I do now that the challenge is over ?? I guess I'll just have to get a new project and see what I can learn from that.
Thanks again
walt


Top
 Profile  
 
 Post subject: Re: Automatic radio model CL -152M silver mica disease
PostPosted: Jun Sat 15, 2019 2:31 am 
Member

Joined: Jun Mon 01, 2015 9:34 pm
Posts: 1407
Location: Greenville, TX
Here is my approach which only requires a scope and accurate sig gen.

I put a 1K resistor and a 100pf cap in series with the transformer and measured the voltage across the resistor as the frequency was varied. At resonance the voltage peaks and I could solve the f squared = 1/4x3.14x3.14x100pfxL.
Knowing L then I could calculate the proper C to resonate at 455kHz. 140 pf was the answer in my case.

_________________
Dale

http://www.dalesantiqueradio.com/


Top
 Profile  
 
Post New Topic Post Reply  [ 23 posts ]  Moderators: Norm Leal, Marcc Go to page 1, 2  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: Chris108, egg and 25 guests



Search for:
Jump to:  


































Privacy Policy :: Powered by phpBB