VT1xx video board -transistor cross reference wanted

[Teletech]

I'm looking at needing to replace the TO3 transistor on the video board of a 131 I'm cleaning up.
Original part is a Motorola MJ3029 or late it looks like they went to a Matsushita 2SC901A.
What are people experienced with using with satisfactory results?
The crosses I found were BU426A, BU526, 2SD418, 2SD807, and BUX13.

 

[Hugo Holden]

Pay no attention to suggested equivalents, it is a matter of checking the data sheets, especially for this application. One equivalent for example, I saw on the net, was listed as a 2N3055 which won't work.

A horizontal output transistor (HOT) is a special part in that it must have a high transition frequency, preferably over 5 to 10MHz and a low storage time to allow it to turn off quickly for flyback. The other import parameters are its collector breakdown voltage (as the is a high voltage peak at flyback), collector -base breakdown voltage and the collector current rating. Also the current gain is important, or in a particular set, the base drive might be inadequate to get it into saturated switching.

If the manufacturers of the VDU put in a 2SC901A as a substitute, I would go for that as a replacement, but if somebody else did, I would not, as its collector voltage ratings are a little lower than the original part (but that might be ok depending on the peak collector voltage in the particular VDU). The 2SC901A is a very good deflection transistor I have used many times. A similar part is the BU104, designed for modest sized monochrome VDU and TV's.

Up spec'd HOT's for color TV work have much higher collector voltage ratings, such as 1300 to 1500V, but often they have a lower current gain, so they may or may not be suitable as replacements in this application if the drive current is not high enough to get them into saturated switching.

It is not really a problem though, because the MJ3029 is readily available on ebay. Watch out though, some there are possibly new manufacture clones that might have small transistor dies in them. However, these original ones made in 1984 are certain to be good (fakes & clones don't come in the aged Fairchild/Siliconix package):

4PCS MJ3029 NPN 5AMP 250V TRANSISTOR | eBay

Find many great new & used options and get the best deals for 4PCS MJ3029 NPN 5AMP 250V TRANSISTOR at the best online prices at eBay! Free shipping for many products!

www.ebay.com

Also these 2SC901A's look perfectly genuine to me.

2SC901A / TRANSISTOR / TO3 / 2 PIECES / (qzty) | eBay

These parts are new and unused.

www.ebay.com

as are these, don't know why the auction said Panasonic, all 2SC901A's are made by Matsushita:

2SC901A Original New Panasonic TO-3 Transistor C901 | eBay

Let us fix the problem for you. We will do our best to get back to you as soon as possible. At Dalbani we like to differentiate between new, previously installed parts (used), and parts made by 3rd party manufacturers.

www.ebay.com

 

[hornbetw]

On October 1st, 2008, Matsushita Industrial Electric Co, LTD renamed itself as Panasonic Corporation. Prior to that, Panasonic was a brand of Matsushita.

 

[Hugo Holden]

On October 1st, 2008, Matsushita Industrial Electric Co, LTD renamed itself as Panasonic Corporation. Prior to that, Panasonic was a brand of Matsushita.

Yes, interesting, that would explain the auction listing, but what I was getting at is , with these early 2SC series vintage H deflection transistors, I have only ever seen them with Matsushita labels on them. They must have stopped making them decades before the company got re-named. I could be wrong but I don't think there is a 2SC901A with Panasonic written on it.

The Worlds first Silicon TO-3 H deflection transistor I think was made by Sony, the 2SC41, for their TV-5-303 set in the very early 1960's. At that time most other makers were using Germanium types. The 2SC901A acts as a replacement for this transistor too.

 

[Chuck(G)]

Back in the day when I needed a replacement for a color TV, I'd use the 2SC1308. It could even be had as a bubble-packaged rack card from the local Radio Shack, complete with insulating washers. It'd probably work in this application.

 

[Teletech]

OK, I crossed my fingers and ordered up a few off ebay. I suppose risking a counterfeit transistor isn't any more risky than and untried substitution.
I'll report back once I've got progress to report.

 

[Chuck(G)]

If those don't work, you can always use the old standby, the 2SC1308. Used in innumerable color TV sets; breakdown is on the order of 1500V.

 

[Teletech]

The Signetics chips from Ebay came in. They worked great and two of my boards are resolved.
I have a couple other boards with unusual issues that I could use some input on:
Board 1, no terminal video, but if I turn up the brightness I can see the raster and overall field looks great, just the video is getting lost along the way.
The VT100 has that provision for injected video and I think that circuitry in confusing me because I'm having some difficulty parsing it. I thought perhaps it was common enough that someone might know what "always breaks" in that case.
Board 2, that one confuses me far more, There is video if I turn up the brightness, but there's a lot of horizontal smearing and several vertical bars of varying intensity. I've not got a clue on this one.
Update on board two, thinking it might just possibly be a failing horizontal transistor and having a spare, I swapped it out and the problem is gone. So, just the one with no video input working for now.