Re: bad bottlecap transistors causing squiggly vectors?

From: Pat Danis <patdanis_at_verizon.net>
Date: Thu Jul 29 2010 - 14:54:01 EDT

Perhaps I should have been more specific.  I don't blindly replace transistors.  If the originals are good, I keep them.  (Too expensive)  If I find a bad one, I do replace them in pairs to make sure the tolerances are the same.  I don't profess to be an expert in electronics but think that you would like to have evenly matched parts.  I'm sure one vendors tolerances are different from another's.  In the description of the wavy lines I referred to, it is hard to determine where the problem lies.  The specific case I am referring to is for a Space Duel monitor I rebuilt.  The cabinet was a project I purchased as non working.  Rebuilt brick, (bad rectifier, fuse block bad and hacked wiring), AR board toasted, and monitor non-working.  After rebuilding the AR and brick and fixing the monitor, I could not be sure the if the problem was due to the monitor or the main board or something else.  I tried another monitor with a jumper harness and the "waves" were much less obvious but still there.  I don't recall the origin of those transistors on the better monitor.  I have also found that the replacement transistors seem to be less tolerant of   Perhaps it could have even been classified as jitters.  I didn't have time to troubleshoot further as I was on a time schedule and had to have it delivered in working in a matter of days.  I was lucky to get it done as it was due to the hacks on the monitor.

I only offered to test a theory I had as a means of contributing to the group.  I will still attempt to document my findings and then submit them here for further abuse/discussion.  I would also like to point out that I do remove and reinstall the original bottle caps if they are still good but 30+ years of heat, smoke, dirt and dust do take their toll on the heat sink compound and I am doing what I can to keep them running for another 30.  Who knows, maybe I'm doing something wrong and I'll find it out.  As far as buying in matched pairs, I don't know if the vendor I purchase from has "matched" sets.  I only purchase bulk quantities and hope that the tolerances are close enough as they came from the same batch.  You're right, I don't have a curve tracer.  Wouldn't know how to use one if I had one.

I still have access to that game and may go by and grab the monitor and test it with a different game.

I also recently found a monitor out of a bulk buy with transistor numbers I wasn't familiar with.  I will dig it out and see what they cross to.  I would be interested in seeing what somebody else was using to get a monitor working.  For all I know, they are direct crosses.  Just wasn't familiar with the part numbers.

Do you have  a source for matched transistors at a "reasonable" price?

Pat

Kevin Moore wrote:

I think Generally speaking it's also a good idea to used matched pairs on your push pulls too. But since buying MP's are not always convenient, and not everyone has a curve tracer to try and match them.  I'd have to agree with Mark though. I doubt that would be your problem. They would/could cause other issues. For example, Walling on Tempest. 

Kevin

On Thu, Jul 29, 2010 at 10:48 AM, Mark Shostak <shostakmark@gmail.com> wrote:

Uh, kind of obvious, but you could put the original TO-3 transistors back in, and see if the problem goes away. If you're like many of us, the parts are still on the bench...

However, IMHO it's unlikely that it's the transistors causing the issue, assuming you replaced them with the original devices and not subs.

Also, rule of thumb in push-pull is to replace _both_ outputs at the same time, and also to replace both drivers when replacing the outputs. This rule primarily pertains to repairs after a failure and not to, "it ain't broke, but I'm fixing it anyway" type activity.

-Mark 

On Thu, Jul 29, 2010 at 10:37 AM, Pat Danis <patdanis@verizon.net> wrote:

I too had noticed that some of my WG 6100s were not as sharp after replacing all the transistors and doing a complete rebuild of all the components.  The lines were a little wavy and not completely straight.  I suspected that perhaps the bottlecap trannies might be an issue but don't have the smarts necessary to make a determination if it was the transistors or something else I might have replaced during the rebuild.  I am going to track my findings in some 6100 rebuilds I will be doing in the next few weeks to see if there is a correlation to the transistors I am using.  I have 2 different sources for the present time.

I will see if there is any visible difference between original, and the 2 sets of replacements transistors after a rebuild.  My month of August is pretty booked up right now but I need to get some 6100s done so I will attempt to get this info posted.  I'll even take video if possible.  No guarantees.

Pat Danis

PJ wrote:

I was looking over Darren Finck's post regarding issues with a G05-802 having amongst a number of things, squiggly vectors.  This tweaks my memory of the issues I had with an Amplifone that had a bad case of twisted distorted vectors on certain objects (see my starwars posts from last spring).  I also had a similar issue on a G05 with original transistors that I figured were getting tired, and once replaced, the issue went away.

 

The Amplifone in question had new transistor pairs on both channels.  Since the original transistor pairs were long replaced prior to my involvement with whatever transistor the previous owner had on hand (literally), I replaced them with the correct parts, and from evidently, the same batch that I used in the G05.

 

What I ended up with was when the drive from the game board was normal, and the gains on the deflection were set higher to fill the screen, the vectors were distorted, like the start and stop rates were bad.  Tweaking the drive from the game board  to a high level, and dropping the gains on the deflection board made the effect less evident.

 

I'm wondering if the 2N3716s and 2N3792s have changed or the specifications aren't what they once were.  Anyone else seen this?

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--------------------------------------------------------------------------- ** Unsubscribe, subscribe, or view the archives at http://www.vectorlist.org ** Please direct other questions, comments, or problems to chris@westnet.com Received on Thu Jul 29 14:54:45 2010