Troubleshooting mystery with Monitor radio.

Page 1 of 2 1, 2  Next

View previous topic View next topic Go down

Troubleshooting mystery with Monitor radio.

Post by NashvilleRad on Thu Jan 05, 2012 11:27 am

I found the discussion and video in the other thread (http://www.tuberadioforum.com/t763-strange) quite interesting ... I too have a 'strange' problem with the Monitor TA-56M radio I'm working on.

I replaced all the caps, checked all of the solder connections (which never really ends), replaced a few out of spec resistors, and still no sound.

With the set making only hard abrubt static noise when rotating the variable cap, I signal traced my way between the Converter and Oscillator and came across a suspect wire that appeared to 'sizzled' on both ends, so I unhooked it and put a jumper on to do a quick check.

The wire runs from the 14Q7 plate (pin 4) of the Converter tube to the Oscillator Coil.

Guess what? When I touch the jumper, the radio plays and tunes just fine! (Please Note: I'm touching the jumper along the insulated length Smile )

Any suggestions with this mystery would be a fantastic help.

Picture of Jumper (shown by red arrows -- the old suspect cable is shown by the yellow arrow and is just pushed aside):



Picture of Schematic with noted run bracketed in red:


NashvilleRad
Member
Member

Number of posts : 93
Age : 52
Registration date : 2012-01-05

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by sprman on Sat Jan 07, 2012 7:49 pm

Replace the wire and see what happens.First ohm out the wire.Check the padder caps to ant to make sure they are not shorted or dirty.When you touch the wire you had capaciance to it .Padders may be out of tune for ant.Sprman

sprman
Member
Member

Number of posts : 365
Age : 63
Registration date : 2008-03-27

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by Resistance is Futile on Sun Jan 08, 2012 1:14 am

Also check the fine wires on the coil, sometimes clean solder can hide bad connection or corrosion.
avatar
Resistance is Futile
Member
Member

Number of posts : 977
Age : 73
Registration date : 2008-03-12

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by NashvilleRad on Mon Jan 09, 2012 12:53 am

Excellent - thanks for the ides. I will check these suggestions as soon as I can.

NashvilleRad
Member
Member

Number of posts : 93
Age : 52
Registration date : 2012-01-05

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by NashvilleRad on Wed Jan 11, 2012 12:09 pm

sprman wrote:Replace the wire and see what happens.First ohm out the wire.Check the padder caps to ant to make sure they are not shorted or dirty.When you touch the wire you had capaciance to it .Padders may be out of tune for ant.Sprman

Still traveling for work, so, haven't had a chance to get back to troubleshooting.

SPRMAN ... if you're in the Nashville area, I may have to ask your assistance at some point - any additional troubleshooting knowledge would be fantastic - and maybe importantly, better test equipment.

By pad caps, I'm presuming the adjustable caps built in for alignment.

NashvilleRad
Member
Member

Number of posts : 93
Age : 52
Registration date : 2012-01-05

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by sprman on Wed Jan 11, 2012 8:08 pm

Hi no they would adjust the ANT .I use a meter .Im south of nashville .Take your time check everything you did.Check to make sure tubes fit tight into the sockets and are in the right places to. Make sure tube pins are clean.Dont mess with any padders.Replace the bad wire with same length.Try wiggling the tube to see if it plays.Sprman

sprman
Member
Member

Number of posts : 365
Age : 63
Registration date : 2008-03-27

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by NashvilleRad on Sat Jan 14, 2012 10:50 pm

Ahhhhhh .... no luck still. I replaced that wire though Sprman. I can jumper from pin 6 to anywhere really - especially past the variable tuning cap straight to the antenna - and get a nice loud and clear signal. Resistances check good on the loop antenna, etc.

May have to take a break on this for a bit.

NashvilleRad
Member
Member

Number of posts : 93
Age : 52
Registration date : 2012-01-05

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by butch on Sun Jan 15, 2012 4:28 am

did you check the osc coil itself for continuity?butch

butch
Member
Member

Number of posts : 27
Registration date : 2008-05-09

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by NashvilleRad on Sun Jan 15, 2012 8:46 am

butch wrote:did you check the osc coil itself for continuity?butch

Hey Butch, yep - verified the readings I had logged this morning ... Primary and Seconday match exactly what's on the Photofact sheet: 0.7 and 6 ohms, respectively. The IF coils and antenna continuity checks are also dead on - and - I took the liberty of replacing that 15 Meg and 22k resistor.

I guess I'm down to the variable cap (?) and looking for continuity/re 'wetting' solder contacts on the associated runs ...

... but, will take a break and give it a fresh look another time - chances are if I've missed it several times, I'll keep missing it.

NashvilleRad
Member
Member

Number of posts : 93
Age : 52
Registration date : 2012-01-05

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by sprman on Sun Jan 15, 2012 10:11 am

Make sure Vari Cap plates are not touching or its not dirty Use alcohol to clean it if its drirty.Post photo of vari Cap .. Sprman.

sprman
Member
Member

Number of posts : 365
Age : 63
Registration date : 2008-03-27

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by NashvilleRad on Sun Jan 15, 2012 10:53 am










NashvilleRad
Member
Member

Number of posts : 93
Age : 52
Registration date : 2012-01-05

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by Bill Cahill on Sun Jan 15, 2012 4:33 pm

Have you tried wiggling tubes?If those are locktal, they are prone to poor connections, and, corosion.
What was the complaint, again?
Any sound at all?
Bill Cahill

_________________
Please also join us here;  http://videokarma.org/index.php
avatar
Bill Cahill
Admin
Admin

Number of posts : 4548
Age : 66
Registration date : 2008-03-12

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by NashvilleRad on Sun Jan 15, 2012 10:14 pm

Yep ... cleaned the sockets and pins as well with some handy electronics cleaner. As I mentioned, I'll take a break from it and come back with a fresh approach.

Thanks for all the help - it's not easy trying to troubleshoot in the virtual world Very Happy

NashvilleRad
Member
Member

Number of posts : 93
Age : 52
Registration date : 2012-01-05

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by sprman on Mon Jan 16, 2012 6:44 pm

Nice pictures tuning cap looks good but clean it and see if that helps.If you have not tryed replacing Osc tube try that.Sprman

sprman
Member
Member

Number of posts : 365
Age : 63
Registration date : 2008-03-27

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by butch on Mon Jan 16, 2012 8:53 pm

does the set play when you touch the rf side of the tuning cap?if it does check out your ant coil for bad connections.the wire is so fine on these coils its easy to solder a wire on and get a bad connection.butch

butch
Member
Member

Number of posts : 27
Registration date : 2008-05-09

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by NashvilleRad on Tue Jan 17, 2012 7:53 am

Hey Butch, it absolutely does play when I touch the RF side - especially at the 'tab' above the alignment pot on the tuning gang. When I jumper directly from the 'tab' to the loop terminal, it's a whole new radio - see pictures and descriptions below.

I'll check the loop connections and the loop itself again - I've looked for little nicks, cuts, opens, gouges, and poor connections ... as I mentioned what they taught us in the Navy - if you've overlooked something 10,000 times, you'll probably miss it the 10,001st time as well!

Layout of the tuning gang:



Primary and Secondary (not in order below) readings are pretty good:

Spec is 0.0 ohms (sorry for blurry picture):



Spec is 1.4 ohms:



Jumper right past it - VOILA! Sound and tuning!


NashvilleRad
Member
Member

Number of posts : 93
Age : 52
Registration date : 2012-01-05

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by NashvilleRad on Tue Jan 17, 2012 4:30 pm

UPDATE (if you're not bored out of your mind with this yet!):

Per Butch - I moved my efforts to the loop and decided to desolder and clean the terminals on the loop template and saw that at the terminal noted by the red arrow, there was some remnant braided wire under the heap of old solder.

Well, that wire had to go somewhere -- so I decided to start the 'jumper leapfrog' game again.

Knowing it wasn't directly connected to the vari cap tab -- this is what I wound up with (which essentially goes to the same RF side of the gang anyway):



The Photofact doesn't discern the primary/secondary taps/connections to the loop, so I'm kinda guessing.

It sounds pretty good (even better when you touch it - just like growing up as a kid).

I suspect the set may have been overheated for a long time or took a pretty good surge making the loop brittle - the oscillator has a few waxy runs on it too.

The only other things: the 50A5 runs kind of hot and the voltages are a little higher than normal. I'm thinking this is a supply issue in this old house.

Then, there's the dial cord, which I'm not looking forward to.

NashvilleRad
Member
Member

Number of posts : 93
Age : 52
Registration date : 2012-01-05

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by Bill Cahill on Tue Jan 17, 2012 7:39 pm

Congrats on the repair. It's a little different, but, hey, if it works.....
Glad you fixed it.
Higher voltage in your house?
Not good.....
Bill Cahill

_________________
Please also join us here;  http://videokarma.org/index.php
avatar
Bill Cahill
Admin
Admin

Number of posts : 4548
Age : 66
Registration date : 2008-03-12

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by NashvilleRad on Tue Jan 17, 2012 9:06 pm

Well, thanks Bill - I'm presuming it's at least part of the repair - I would like to find a more clear picture that may show how and what that may have been wired to - it was obviously there at some point. Strange.

The voltage in the house - its an old turn of the century Belmont 'shotgun' style here in Nashvile - not a single grounded outlet in the place, and it's been made into apartments, and the wiring is kind of dicey. There's just no telling ...

NashvilleRad
Member
Member

Number of posts : 93
Age : 52
Registration date : 2012-01-05

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by butch on Wed Jan 18, 2012 3:30 am

i think the unused terminal you found is just a hookup for an external ant.i think your problem is in the ant. coil as your jumping around it.butch

butch
Member
Member

Number of posts : 27
Registration date : 2008-05-09

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by NashvilleRad on Wed Jan 18, 2012 6:47 am

Hey Butch, indeed it is a nice little 'patch' as Bill noted ... agreed though on something screwy with/or involving the antenna.

It's frustrating because even detached from the radio hookups, the continuity checks out as noted in a previous post.

And since I had it detached, I looked around in the basement for another old similar loop just for grins, but will maybe have to wait for the next flea market and hope to get lucky.

There are some other notes I've been pondering ...

There is a lug on the back for an external antenna - I believe there should at least be a 'convenient' lead hooked up to it (?):



When I first got the radio ($2 @ Fairgrounds!), there was one unattached wire on the top stanchion shown here:



These are the chassis-mounting stanchions for the oscillator coil underneath. The solder connection was heavily oxidized and the insulation on the wire dry-rotted and flaking everywhere so I removed it.

Indeed, looking at both stanchions, it appears as if something may have been attached to both at some point - but it's not very intuitive what that could have been from a circuitry standpoint - or maybe I'm not reading the schematic very well.

NashvilleRad
Member
Member

Number of posts : 93
Age : 52
Registration date : 2012-01-05

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by NashvilleRad on Wed Jan 18, 2012 8:24 am

OK guys ... I am a complete goof.

I went back and looked at pictures of the wiring layout to the antenna when I first opened it - and re-arranged the wiring to match.

You know ... it really helps to have the primary loop correctly connected! And indeed Butch and Sprman - those loop wires are tiny and hard to see.

I'm GLAD I took those pictures! I'll take even closer pictures as well next time.

However, I still can't make out what the wiring from the oscillator stanchion(s) go to or what they were for ...

NashvilleRad
Member
Member

Number of posts : 93
Age : 52
Registration date : 2012-01-05

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by NashvilleRad on Wed Jan 18, 2012 10:57 am

After my egregious 10,001st overlooking of the most obvious, I still have one final piece to the puzzle I mentioned above.

And that is this 'mystery' wire hooked up to the oscillator chassis stanchion ... shown here:



Here it is on the Photofacts sheet with braided blcak-and-white insulation extending inside the chassis - a little hard to see:



Is that ..... this?



What is that? A tickler?

NashvilleRad
Member
Member

Number of posts : 93
Age : 52
Registration date : 2012-01-05

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by Bill Cahill on Wed Jan 18, 2012 2:24 pm

It's part of the oscilator coil on the other side. I see at least part of your problem... Your antenna wirring is shot, and, shorting to chassis. You need to replace those bad wires. I wonder what the condition of the rest of the wiring is like. It could be dangerous.
Don't connect an external antenna, and, especially NOT a ground. That would be extremely dangerous!
May we see the underside of your chassis?
Thanks.
Bill Cahill

_________________
Please also join us here;  http://videokarma.org/index.php
avatar
Bill Cahill
Admin
Admin

Number of posts : 4548
Age : 66
Registration date : 2008-03-12

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by NashvilleRad on Wed Jan 18, 2012 3:14 pm

Hey Bill, that wiring has been replaced - the above was a picture I was just lucky to have remembered I took when I first cracked open the radio a while back.

I added it here to show there was actually something wired to that stanchion at some point - where that old rotted yellow wire was - and hopefully figuring out where that's supposed to go is the last piece of the puzzle hopefully. The SAMS sheet shows it running back into the chassis ...

The underside, in its current state - new capacitors and new (temporary test) wiring is in the very first picture of the thread.

NashvilleRad
Member
Member

Number of posts : 93
Age : 52
Registration date : 2012-01-05

Back to top Go down

Re: Troubleshooting mystery with Monitor radio.

Post by Sponsored content


Sponsored content


Back to top Go down

Page 1 of 2 1, 2  Next

View previous topic View next topic Back to top

- Similar topics

 
Permissions in this forum:
You cannot reply to topics in this forum