Looking for a replacement part.

@robotbuilder Now if I can find a replacement.

@robotbuilder BINGO, excellent work. In fact many folks who resurrect these old devices just automatically replace all the capacitors as they will fail over time, and debugging them can be a problem. I have never seen one like that before however.

Hi @mtlatc,

   Now if I can find a replacement.

12pF and 15pF ceramic capacitors are off the shelf parts .. shouldn't be too difficult.

  As an example of what to look for - NOT a recommendation of specific supplier or product :

https://www.aliexpress.com/item/1005004983663190.html

Best wishes,

Dave

@mtlatc The challenge will be to find a non SMD in that size. Maybe solder an SMD to a tiny piece of breadboard and then solder on leads to the breadboard. Here are some I found, but note the date, Mar 23 - Apr 17. https://amz.run/6KLQ NOTE, that is a Canada link, change URL as appropriate for yout country.

@zander @robotbuilder @davee I'm being told this is the replacement for that part...I have no clue if this is 100% correct or not.  I know what's on the drawings, but this guy has fixed these in the past.

https://www.pchub.com/uph-inductor-inductor-color-loop-axial-lead-14w-33uh-al0307-3r3k-p77788

@mtlatc That's not it, it's a 12pF capacitor that you need. As pointed out in the following post.

https://forum.dronebotworkshop.com/postid/37154

Posted by: @zander

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@mtlatc That's not it, it's a 12pF capacitor that you need. As pointed out in the following post.

https://forum.dronebotworkshop.com/postid/37154

 

Texas Instruments TI-99/4A Repair (Wave/Raster Lines) | nIGHTFALL Blog / RetroComputerMania.com (nightfallcrew.com)

It's all these differing links (offering solutions) that are making me crazy.......

@mtlatc Post 37154. Did you look at it? Do you understand what you are seeing? It's your exact part, it's a 12pF cap. END.

Hi @mtlatc,

   The circuit I showed is a tiny clip from what looks like as can of the original TI99/4 manual ... hand-typed and hand-drawn schematic that showed up when I Googled "TI99/4 Console Schematic"

Your photo showed an adjustable inductor, and a metal can device that looked like a crystal, though I couldn't see the printing to check it.

The damaged component could easily be a capacitor ... very unlikely to be an inductor .. as I suggested before.

Looking at the schematics, I noticed a number of the digital components had inductors in series with the power (+5V) lines ... it is possible that these have a habit of failing ... but that is a very different part of the circuit. They are used to reduce stray radio transmission.

e.g. L600 supply to the microprocessor TMS9900 ...

As I said, the real test is to trace out the circuit, and see if it agrees with the circuit snip I provided previously. If it does, then you need that capacitor, not an inductor!

--------------------

And by the way, when Ron @zander mentioned replacing all capacitors, I think he meant electrolytic capacitors, which tend to fail by drying out ... non-electrolytics tend to be more reliable,although occasional failures are always possible. Your damaged component is a non-electrolytic, but has clearly suffered some mechanical trauma.

Best wishes, Dave

Posted by: @zander

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@mtlatc Post 37154. Did you look at it? Do you understand what you are seeing? It's your exact part, it's a 12pF cap. END.

Yes Sir. I absolutely looked at it.  But, if you look at the photo's from my link posted below, those are also my exact part....As you can see I asked him about that exact part. 

So we have two differing post about what appear to be the same part. -- I'm by no means smart enough to know which post is correct.  I'm just trying to put as much information out here so people can provide their thoughts.

Hi @mtlatc,

The component in your original photo looks a thin 'flat' part, but I can only see one side. Are both sides flat? If so, this matches the general capacitor structure of two metallic plates, separated by a flat insulator.

The photo in the repair report has a definite circular bulge, which makes the story that it is an inductor more plausible.

Does your damaged part have the same bulge on the other side?

Best wishes,

Dave

@mtlatc 

According to the link I gave the component in question was a large, fat 12pF ceramic capacitor so I guess any 12pF ceramic capacitor would do.  The link didn't actually show the replacement.

Posted by: @davee

↑

Hi @mtlatc,

The component in your original photo looks a thin 'flat' part, but I can only see one side. Are both sides flat? If so, this matches the general capacitor structure of two metallic plates, separated by a flat insulator.

The photo in the repair report has a definite circular bulge, which makes the story that it is an inductor more plausible.

Does your damaged part have the same bulge on the other side?

Best wishes,

Dave

Here are two more photos. I had to get them under the size limitation so I hope you can see what your looking for.  But, yes there does appear to be a "bulge" on one side.

@mtlatc Ah, that's the first view with the bulge. However that does not explain the other post. I would buy one of each and see what works.

Hi @mtlatc ,

That new picture does complicate the situation.

Sorry, but I think the only way to solve the situation is for you do some actual circuit tracing to identify  the parts and compare with the schematics. Starting with the schematics, you probably only have to trace 4-5 parts.

Best wishes,

Dave