1987 Toshiba CRT vertical section caps and LCR meter ESR readings

[ckrtech]

Hey guys -

So I finally picked up an LCR meter (DE-5000) to start doing readings and boost understanding a bit.

I have a Toshiba CRT with partial vertical collapse. I have no service manual. I assume caps are circa 1987, but there is quite a mix in brands in a small area.

Probes calibrated. Caps discharged. Readings attached.

1: I am primarily interested in measuring ESR @ 100kHz, correct? It seems like I was getting some pretty large numbers relative to what I would expect. Are they really that bad? I included other frequencies for reference.

2: Why am I getting OL on that 100uf chemicon? Even if it is super small, shouldn't I get a reading?

3: What are your thoughts on the numbers I provided? Which ones should I replace and why?

4: What replacements should I use? I've done recapping many times before and have my favorites, but I am unfamiliar with Marcon.

I assume at the very least that the 250V Marcon and the single Nichicon should be replaced.

[R_J]

Re: 1987 Toshiba CRT vertical section caps and LCR meter ESR readings

Are you measuring the caps in circuit? Why not post pictures of the tv and post the model and chassis number, there is likely a schematic around.
When you say partial vertical collapse, is there also retrace lines at the top of the screen? if there are then it is likely the 4.7/160 or the 2.2/250 that are bad

[ckrtech]

Re: 1987 Toshiba CRT vertical section caps and LCR meter ESR readings

I actually pulled the caps prior to obtaining the LCR meter, so those measurements are from out of circuit. Model is Toshiba CF317. Chassis 8710. October 1987. I can add a photo of what it looks like tomorrow.

I believe there were perhaps two retrace lines to help "kick-off" the start of the picture. I wasn't sure if I should call them retrace lines as whatever they were was only at the top of the image as I didn't see them in the remaining picture when sending a signal to the RF input - as opposed a run of retrace lines throughout the image from top to bottom like what you would see if the screen on the flyback was up to high.

Apparently a quite common problem with some Toshibas is the bootstrap capacitor that tends to be 2.2uf. I certainly have a candidate for that one. Would be nice to find the schematic around for educational purposes.

[Andrew F. Ali]

Re: 1987 Toshiba CRT vertical section caps and LCR meter ESR readings

I would recommend e-cap change out of all the e-caps in the vertical section even if their readings seem to be OK. Is there any pre-sets to adjust vertical height and linearity? Then spray them out with some WD-40 and stroke them fully cw and the ccw. Mark the original positions before turning them to reset them at their original positions. Look for cold solder joints and firm them up.

[ckrtech]

Re: 1987 Toshiba CRT vertical section caps and LCR meter ESR readings

Sounds like a plan. I am doing a full recap on a Sony set, and I figured I would order caps for the Toshiba along with the Sony caps once I have their values. Easy drop in the bucket to just refresh all eight of the Toshiba ones. There was one larger sized cap in the section that I didn't pull that seemed to have a fairly low ESR when I measured it in circuit. I was planning to leave that one.

I did mess around with the vertical size pot a bit to see if I could expand it (after a bit of contact cleaner). While the pot did make changes, the range just wasn't there. Hopefully the recap will fire the image into a super overscan of sorts, and I can dial it back down to where it should be.

[Andrew F. Ali]

Re: 1987 Toshiba CRT vertical section caps and LCR meter ESR readings

If the re-cap does not fix your problem, then the Vert Out IC on the heat sink would be the culprit. Good luck.

[ckrtech]

Re: 1987 Toshiba CRT vertical section caps and LCR meter ESR readings

Thank you, Andrew.