Hi gang...yes Old TV Destructo here! Actually, I'm in a good place with this one. I was conservative and took my time with the HV capacitor replacement and I have a nice bright picture on a fairly new RCA replacement CRT. A raster is present. All of the wax caps have been replaced. I have replaced several out of spec resistors but honestly, I haven't tested all of them. I plugged in my pattern generator (it is working...tried it on another TV) and there's no signal getting through. The tuner is clean as are all of the control pots. All the tubes have tested good. There's a slight buzz/whistle on the speaker that disappears when I go from channel 4 on the TV to another channel even though my generator does not produce an audio signal. This makes me think something might be getting through or at least that my channel setup and the coaxial connection is OK.

I want to be very conservative and not mess this up like I did my RCA 721 when I started moving coil slugs and the like without understanding what I was doing. What would be the most basic steps to begin to troubleshoot this issue?

Thanks all,
Chris

Honestly this sounds like a known issue with some of these Motos where the video detector diode fails...When that happens you get no video and weak sound.

If you have a line isolation transformer to power the set with, you could try injecting video at the output of the detector. If you have a pattern generator that can output on the old IF frequencies (like a B&K 1077 Analyst) you can try injecting IF at the ant terminals or 1st IF and see if it gets through.

Yup I have 6 of those Motorola sets and 2 of them needed detector diodes had no video or sound, new germanium’s and all was history.

Let me also add that I have been down that road. That 1N34 is often bad. The good guys here steered me to that many years ago. The arrow points to the can which has the diode inside. The other picture is what that diode looks like.

Let me also add that I have been down that road. That 1N34 is often bad. The good guys here steered me to that many years ago. The arrow points to the can which has the diode inside. The other picture is what that diode looks like.

Thank you so much everyone for your generous answers! What should be the replacement diode for this swap?

...and I'm sorry it's the TS-4H chassis.

We ran into a certain line of GE 19" BW portables that were chronically popping the vid det diode. The fix was to put a 680 ohm resistor in series with the diode. Totally cured the problem. Why they were popping remains unknown. Same fix would probably work for your Motos.

(Edit.) Coulda been 560 ohm, hard to remember for sure.

Thank you so much everyone for your generous answers! What should be the replacement diode for this swap?

First thing to NOT use is a 1N4007 diode. 1N34, 1N60, 1N4148... just about any signal diode will work. eBay may not be the best place to find parts because of fake/counterfeit parts. But these diodes are easy to come by. I would take a chance on "The Auction Site" if that is the direction you want to go.

"But wait, there's more!" If you PM me with your address, I will send you a few in an envelope, no charge, no strings attached. Happy New Year!

First thing to NOT use is a 1N4007 diode. 1N34, 1N60, 1N4148... just about any signal diode will work. eBay may not be the best place to find parts because of fake/counterfeit parts. But these diodes are easy to come by. I would take a chance on "The Auction Site" if that is the direction you want to go.

"But wait, there's more!" If you PM me with your address, I will send you a few in an envelope, no charge, no strings attached. Happy New Year!

Amazon has 1N34A diodes. Will that work?

Amazon has 1N34A diodes. Will that work?

Yes.

1n34 or 1n34a will work just take note of where the band goes.

I have a parts chassis and removed and tested the diode and it tested good. The diode in the working chassis was a General Electric replacement and tested bad. I replaced the bad diode with the old but tested good diode and tried to send a crosshatch signal through. No change. I did order 1N34A diodes from Amazon that’ll be delivered Tuesday. I’ll try one of those and see if there’s any change.

First thing to NOT use is a 1N4007 diode. 1N34, 1N60, 1N4148... just about any signal diode will work. eBay may not be the best place to find parts because of fake/counterfeit parts. But these diodes are easy to come by. I would take a chance on "The Auction Site" if that is the direction you want to go.

"But wait, there's more!" If you PM me with your address, I will send you a few in an envelope, no charge, no strings attached. Happy New Year!

Oh my…thank you so much! I’ll try the new ones I ordered and if I have no luck I will contact you! Thanks again

Amazon has 1N34A diodes. Will that work?

Read the reviews... some people complain that they actually got silicon rather than germanium diodes. :thumbsdn:

jr

Read the reviews... some people complain that they actually got silicon rather than germanium diodes. :thumbsdn:

jr

I think you are correct and I looked at Digikey and Mouser and they're listed as obsolete components and not in stock.

Chris, I will send you some diodes. I checked them with the diode function of my Fluke meter and they seem to be OK. They are new, probably new manufacture. I have had them for a while. Hope this fixes your set.

I did have an unusual problem with one of my vt71 and after putting the new diode in it turned out that someone didled with the alignment screws at the head of the chassis IIRC the 4h or 4j has those adjustments but the ts18 don’t if the diode don’t work and everything else is good to go then check the schematic for channel 3 slug on the chassis it didn’t take much to get it working. Just another thought on these sets. Those germanium diodes should check under 3 and indicated good.

Chris, I will send you some diodes. I checked them with the diode function of my Fluke meter and they seem to be OK. They are new, probably new manufacture. I have had them for a while. Hope this fixes your set.

Can't thank you enough!

https://www.ntepartsdirect.com/ENG/PRODUCT/1N60A?gclid=CjwKCAiA-8SdBhBGEiwAWdgtcHXMePB234UV3wZva5imk2GmdLTuWoCsQQh aTMGFiLUBRVIJ9LfEthoCeeIQAvD_BwE

Chris, I will send you some diodes. I checked them with the diode function of my Fluke meter and they seem to be OK. They are new, probably new manufacture. I have had them for a while. Hope this fixes your set.

I do have some 1N4148 diodes and put one in...still no change...tried both channel 3 and channel 4 signal output.

I do have some 1N4148 diodes and put one in...still no change...tried both channel 3 and channel 4 signal output.

Get any sound ? Are all the tubes good?

Get any sound ? Are all the tubes good?

All the tubes tested good on a Seco 107. Yes I get sound that responds to volume changes specific to the channel I'm feeding through so if I'm feeding the crosshatch into channel 3 and I flip the TV tuner to channel 4, the sound disappears. Mind you, as I posted before, my Leader LCG-396 does not produce an audio tone along with the video pattern but, something is getting through to the audio...a high pitched dirty tone that goes up and down with volume changes and fades in and out if I move the fine tuning. I have moved both the channel 3 and 4 adjustment slugs around a bit but not so far I would lose my frame of reference of their initial position. At most it was half a turn for each in either direction. The audio sound faded in and out when I moved them and then returned them to original position. No picture or a hint of a picture in there. I've also played with the horizontal and vertical hold controls. Still, no image.

Just for additional info and to be certain I dont have the feed into the TV moronically incorrect, the leads on my coaxial converter are connected to the two terminals on the back of the TV marked "A" which I assume means antenna. There is a third screw terminal marked "G" between them I assume is ground. I do not have anything connected to that.

Yes I remember there is 3 screws and you are using the 75-300 matching transformer with cable screwed on to that. Long as the 3 6ag5 tubes are good and if the diode is good and all else failed I would trace back from pin 2 of the crt and look at what it passes maybe you can pick something up along there and as for the slug yes keep good track where you are when turning them. Those sets are pretty simple I’m sure you will nail it shortly. Don’t remember which tube is the video out but check around that tube. Things that are responsible for video. 6au6 video amp.

May want to use a sound capable signal source to check sound circuits are functioning properly.

Also not really important but this set can directly accept 300 or 75ohm antenna hookups. The outer screws are for 300 and IIRC the top screw and center G terminal are used for 75 ohm center and shield respectively. (I may have too and bottom mixed up, check literature before using the 75 ohm direct connection.) Not really that important, but interesting.