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


It is currently Nov Tue 30, 2021 1:01 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 21 posts ]  Go to page 1, 2  Next
Author Message
 Post subject: When it still won't work
PostPosted: Jun Sat 13, 2020 3:16 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 10854
Location: Beaver Falls, PA. USA
Many posts on the Forums involve projects that still have problems, even after component replacement. Here are some suggestions:

First, go back and check your work. It is very easy to make a wiring error, having something connected in the wrong place; we have all done it. As a former coworker, now RIP, used to say; "If the set develops another problem after you have worked on it, go back and find the problem that YOU put in". It might be as simple as a broken wire. Don't overlook anything.

Second, watch out for incorrect component substitution. It is very easy to misread a color code or capacitor marking, especially on new capacitors with a code number instead of a printed value.

Third, check the coils, speaker fields, and transformers. Open windings are common in Philco sets, but I have seen them in other makes.

Fourth, the oscilloscope is your friend. They are a big time saver on things like TV sets and communications equipment. All B+ lines should be free from any signals and ripple, and all test points should have the proper signals, at the proper amplitudes.

Lastly, check the ground connections. It's not uncommon to find that one has a high resistance, or is completely open, due to corrosion; this is particularly true of tube socket grounds. The multi-pin terminal strips on 1960s Zenith TV sets, for example, often break loose at the ends. Don't try to resolder grounds with a small iron; use something big like a Weller D550. Kit-built equipment with PC boards often rely on the board mounting screws to complete the ground connections, and they often work loose.

_________________
Tim KA3JRT


Top
 Profile  
 
 Post subject: Re: When it still won't work
PostPosted: Jun Sat 13, 2020 11:30 pm 
Member
User avatar

Joined: Dec Tue 23, 2014 6:51 pm
Posts: 2412
Location: N. Palm Bch, Fl.
Very Good. I would add 1 more though. This should be a cut, paste, and print for some and for newbies. Your first is mine because it has burned me before. It is time consuming because you have to concentrate and compare what you see to what the schematics says. So many post here end up with component soldered to the wrong tube pin or not soldered at all.
I bought my O scope for a TV horz probem and it really helped with 2 radio alignment problems. I love my scope.
I would add when above fails; Start a post here with HELP. If you go through 1 to 5, you may not have to though.

Freeman


Top
 Profile  
 
 Post subject: Re: When it still won't work
PostPosted: Jun Sun 14, 2020 7:59 am 
Member
User avatar

Joined: Oct Mon 02, 2017 8:53 am
Posts: 1659
Location: Panama City, FL 32401
Checking current drain can tell much about how a radio is working. Recently I've been checking current drain in my radios. One Zenith Royal 50L I have works fine,or so I thought. When it showed unusually high current drain I cleaned both battery contacts. One of the wires was quite corroded. I stripped the wire then soldered it back on. Now the current was much lower and typical of what it should be.


Top
 Profile  
 
 Post subject: Re: When it still won't work
PostPosted: Jun Sun 14, 2020 12:37 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 10854
Location: Beaver Falls, PA. USA
Another thing that I forgot to mention; just about every old radio will benefit from a careful realignment. It's not uncommon to find that the IF transformers are way out of resonance, which will greatly reduce the gain. Some multi-band radios have a definite sequence for the front-end alignment, and the instructions must be followed.

Also, don't overlook tubes as a source of trouble. Some substitutes just will not work, especially in critical front end circuits. Some tubes may refuse to oscillate under certain conditions, especially when they get a little weak; 6A7 and 6A8 tubes are notorious for this.

Audio output tubes can be mystifying trouble makers when they go gassy or get secondary emission, which can cause the plate current to "run away" . At the price of some tubes, it is easy to hunt for other problems, in hopes that the tubes aren't the cause. Any tube that has red plated is suspect. Of course, this assumes that other causes have been corrected, such as leaky coupling capacitors and biasing problems. Amplifiers with direct coupled driver circuits, such as Macintosh, are especially sensitive to tube problems.

_________________
Tim KA3JRT


Top
 Profile  
 
 Post subject: Re: When it still won't work
PostPosted: Aug Mon 03, 2020 8:33 pm 
Member
User avatar

Joined: Nov Fri 10, 2006 12:24 am
Posts: 3044
Location: Thornhill, Ontario, Canada
As I've said here several times... always test the radio (or amplifier) after EACH component replacement... no optimistic batch replacements!
That said, again... years ago, I refurbished a radio which then worked perfectly... I put it on the shelf with no plans except to fire it up now and again just for fun.
Did this last year, it worked fine, but I decided to check what I had done close to a decade earlier... Surprise, there was an un-soldered joint on a replacement capacitor... just bent around and crimped! OMG! How on earth...? Now fixed, and all the others checked.
So, I never put more than one new component in place at a time, soldering both ends! Indeed, I even solder one end before fitting the other end!
Cheers,
Roger

_________________
Roger Jones,
Thornhill, Ontario
Ontario Vintage Radio Assoc. http://www.ovra.ca


Top
 Profile  
 
 Post subject: Re: When it still won't work
PostPosted: Aug Tue 04, 2020 8:43 pm 
Member

Joined: Jun Sat 09, 2007 8:14 am
Posts: 5171
Location: Melbourne, Florida
Any time I have something that doesn't work I troubleshoot. That includes things I've never seen before or something I "fixed" that didn't quite make it.

RRM


Top
 Profile  
 
 Post subject: Re: When it still won't work
PostPosted: Aug Sun 16, 2020 2:48 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 10854
Location: Beaver Falls, PA. USA
Some folks persist in trying to get an old piece of equipment working without doing any recapping. Those of us who worked on the stuff when it was relatively new know about the problems with capacitors, and there is no easy way out. The changeover to Mylar capacitors was gradual, and some stuff from the 1960s still had a few paper capacitors; mainly in the form of "Black Beauties" . Even the "maroon drops" from the late 1950s are failing now. The early transistorized equipment is full of small electrolytic capacitors, which are often open or leaky. New capacitors are cheap, and the time spent on replacement will pay off.

_________________
Tim KA3JRT


Top
 Profile  
 
 Post subject: Re: When it still won't work
PostPosted: Sep Mon 28, 2020 1:26 pm 
Member
User avatar

Joined: Nov Wed 30, 2016 7:35 pm
Posts: 11291
Location: Sunbury, Ohio 43074
My favorite is some "mylar looking" capacitor that simply isn't mylar at all. Also there were, and still are, some orange drop "look alike" caps that are just as bad. Unless you are SURE it's actually a mylar, or other film type, just replace it. New caps are quite cheap, and much higher voltage rating while being half the size of the old ones.

_________________
Preserving the hist. of electronics, one boat anchor at a time! :)
https://www.bbtvtestequipment.com


Top
 Profile  
 
 Post subject: Re: When it still won't work
PostPosted: Sep Mon 28, 2020 9:51 pm 
Member

Joined: Jan Tue 07, 2020 1:41 am
Posts: 4369
Location: Belleview, FL 34420
And, finally if cannot get it working? .............................Sell it to a tech.

_________________
NAVY JACK FLAG- 'Don't Tread on Me'


Top
 Profile  
 
 Post subject: Re: When it still won't work
PostPosted: Sep Mon 28, 2020 10:06 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 11097
Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
Tim Tress wrote:
Some folks persist in trying to get an old piece of equipment working without doing any recapping.


And ..... here's where I always feel the need to jump in.

Recapping is fine, even necessary in certain circumstances, no question about that.

However .........

Wholesale shotgun recapping without doing any troubleshooting is one of the most common lead-ins to "after service" problems that I have read about on these forums. These issue usually seem to happen to newbies who have been scared into wholesale recapping by the old-wives tales about certain death, fires, devastation if they don't.

So .... how about

- careful test
- repair to make "work" in some fashion
- decide about further work needs (restore, store and look at it etc)
- and then move on.

There is NOTHING WRONG with carefully testing a piece of electronics and doing any necessary repairs before replacing a whole pile of parts en-masse in a restoration project.


Top
 Profile  
 
 Post subject: Re: When it still won't work
PostPosted: Sep Tue 29, 2020 1:03 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 39548
Location: SoCal, 91387
If you have tried and tried to get it to function, and it stubbornly refuses to give you that triumph, a temporary emotional satisfaction can be obtained by deftly throwing the damn thing out the window! :wink:

_________________
\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins/////////////////////////


Top
 Profile  
 
 Post subject: Re: When it still won't work
PostPosted: Sep Tue 29, 2020 1:08 am 
Member
User avatar

Joined: Nov Wed 30, 2016 7:35 pm
Posts: 11291
Location: Sunbury, Ohio 43074
Quote:
- careful test
- repair to make "work" in some fashion
- decide about further work needs (restore, store and look at it etc)
- and then move on.

*put it back on the bench a month later
*troubleshoot it again, because you have no clue what you already did to it
*Fix it .... the end. OR
*it won't be fixed. Get a 16lb sledge from the garage and pound it to dust. The end.

_________________
Preserving the hist. of electronics, one boat anchor at a time! :)
https://www.bbtvtestequipment.com


Top
 Profile  
 
 Post subject: Re: When it still won't work
PostPosted: Sep Tue 29, 2020 1:10 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 11097
Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
Barry H Bennett wrote:
OR
*it won't be fixed. Get a 16lb sledge from the garage and pound it to dust. The end.


LOL ... does this happen to you often?

Seriously .... I always fixed them to be working unless I cannot find a part or ...... in one and only one case because I could not fix it.


Top
 Profile  
 
 Post subject: Re: When it still won't work
PostPosted: Sep Tue 29, 2020 1:11 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 39548
Location: SoCal, 91387
Barry H Bennett wrote:
OR
*it won't be fixed. Get a 16lb sledge from the garage and pound it to dust. The end.

My method requires less effort... :wink:

_________________
\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins/////////////////////////


Top
 Profile  
 
 Post subject: Re: When it still won't work
PostPosted: Sep Tue 29, 2020 3:02 am 
Member
User avatar

Joined: Mar Sun 22, 2020 5:56 am
Posts: 2041
Location: Arvada, CO, 80004
Barry H Bennett wrote:
Quote:
*it won't be fixed. Get a 16lb sledge from the garage and pound it to dust. The end.

Wow Barry! I never knew you were a sucker for brute force!

_________________
Electronics are filled with smoke. It’s my job to put the smoke back in when they fail.
Cheers,
Jay


Top
 Profile  
 
 Post subject: Re: When it still won't work
PostPosted: Sep Tue 29, 2020 6:11 pm 
Member

Joined: Oct Sun 18, 2015 2:49 am
Posts: 410
Location: San Angelo, TX
My two cents worth. If you remove some component, MAKE A DRAWING of it and connection points! Pictures are good, but I still make drawings because wires crossing under each other get lost. Denis


Top
 Profile  
 
 Post subject: Re: When it still won't work
PostPosted: Sep Tue 29, 2020 9:32 pm 
Member
User avatar

Joined: Nov Wed 30, 2016 7:35 pm
Posts: 11291
Location: Sunbury, Ohio 43074
John Bartley wrote:
Barry H Bennett wrote:
OR
*it won't be fixed. Get a 16lb sledge from the garage and pound it to dust. The end.


LOL ... does this happen to you often?

In the fiery days of my youth, it used to. I lost several auto repair tools hurled into orbit, apparently. But I"m much better now. ;-)

_________________
Preserving the hist. of electronics, one boat anchor at a time! :)
https://www.bbtvtestequipment.com


Top
 Profile  
 
 Post subject: Re: When it still won't work
PostPosted: Sep Tue 29, 2020 11:48 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 11097
Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
Barry H Bennett wrote:
John Bartley wrote:
Barry H Bennett wrote:
OR
*it won't be fixed. Get a 16lb sledge from the garage and pound it to dust. The end.


LOL ... does this happen to you often?

In the fiery days of my youth, it used to. I lost several auto repair tools hurled into orbit, apparently. But I"m much better now. ;-)


LOL ... I sympathise. About twenty some years ago I needed my first bifocals. I allowed myself to be talked into a pair of reading glasses because my long distance vision was pretty good. I'm not easily irritated and never have been, but those reading glasses did something to me ... perched on my nose .. always there ... just underneath my distance vision line of sight ... sllding down my nose when I perspired ..... arrghhh !! They died on the shop floor under a 2-lb sledge and I went to buy full bifocals ... and loved them from the first second I slid them on :)

...


Top
 Profile  
 
 Post subject: Re: When it still won't work
PostPosted: Sep Wed 30, 2020 7:51 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 10854
Location: Beaver Falls, PA. USA
Besides filter capacitors, the one which should be replaced is the coupling capacitor to the output tube grid (or grids, if it has push-pull outputs). This will be enough to verify the operation, before more work is done. It's not uncommon to find more than one problem.

_________________
Tim KA3JRT


Top
 Profile  
 
 Post subject: Re: When it still won't work
PostPosted: Sep Wed 30, 2020 8:10 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 11097
Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
Tim Tress wrote:
Besides filter capacitors, the one which should be replaced is the coupling capacitor to the output tube grid (or grids, if it has push-pull outputs). This will be enough to verify the operation, before more work is done. It's not uncommon to find more than one problem.


I can get on board with this. It's sensible.


Top
 Profile  
 
Post New Topic Post Reply  [ 21 posts ]  Go to page 1, 2  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 7 guests



Search for:
Jump to:  




































Privacy Policy :: Powered by phpBB