Question(s) with my first brand used SE/30, hopefully a restoration story...

[shieldwolf]

I am trying to restore + mod an SE/30. I have done some work to the logic board and will have some questions about that to post in this thread after I do some due diligence. My first question relates to the analog board. I started by resoldering the connectors and any suspicious looking joints. While doing this I lifted a pad on the TDA1170N (connects to a capacitor, don't remember right now which one.) I put the pad back and resoldered, trying to blob it back to the trace (important later.)

On testing I was greeted with a centered horizontal line. A troubleshooting guide lead me to think the TDA1170N had failed. The original is an SGS, the new one is a Telefunken (the ebay listing was for SGS, don't ask me.) After replacing the chip and doing continuity checks, I realized the problem was likely that I hadn't made good contact from the lifted pad. I exposed more trace and bodged to get good connection.

At this time I also recapped the analog board for good measure. In doing this, I replaced C12 (it had a bulge and leaked when touched even though it was a film cap?) The part I used for this capacitor is a PP cap (R76PI233050H3J .) It should be fine with temperature range, capacitance, and lead spacing is perfect. If I understand PP caps correctly, it should have lower esr and might cause issues later at high temperatures, but shouldn't be an issue at the short term open case testing phase at least.

I am now getting horizontal lines that flicker?, jitter?, I don't know the right word, please see the video.

Because it is so easy to lift pads on this board, and the heat sensitivity the datasheets for TDA1170N talk about, I am hesitant to put the old chip back. I would like to know if this is just an adjustment issue (I have tools for that on the way,) or if there is anything else I should be looking at before I proceed like a bull in a china shop. Before I started the picture was good to begin with and my original intention was to address the solder joints of the connectors and recap the board for maintenance.

 

[This Does Not Compute]

If you're finding the pads on your analog board are getting to be overwhelming, it may be worth considering just replacing the whole PCB entirely. Kay has a BOM linked there too and most of the parts can be bought new/NOS.

 

[shieldwolf]

If you're finding the pads on your analog board are getting to be overwhelming, it may be worth considering just replacing the whole PCB entirely. Kay has a BOM linked there too and most of the parts can be bought new/NOS.

I may have seemed unclear. Please know this is not a rant, nor am I upset at the suggestion. My intention is to clarify. I'm not so much overwhelmed as seeking advice from those more experienced. The tda chips i bought are nos, i just felt a bit bait n switched by the seller over the brand, that has nothing to do with the forum or its members though.

I don't know if there are slight differences in the tda brands that are causing the issue. I brought it up for transparency in the case that it is a problem.

I don't know if that issue is caused by the screen displaying too wide or too far to the left on the tube (adjustment.)

I don't know if there is something else that may be causing the issue that i could test or check.

I don't know what to call the type of artifacting or whatever that the randomly flickery horizontal lines are.

My intention here is to better understand the problem, and the solution(s) for the fun of it, the education, and future maintenance. I may later want or need to replace the board, but for troubleshooting, I am hoping to not damage it too much by just going at it like a gorilla. the board is actually in seemingly good shape, just old and single sided.

 

[This Does Not Compute]

Understandable. It sounded like from your original post that you were having trouble with pads lifting, hence the idea of replacing the whole PCB. If yours is in good shape otherwise then that's likely unnecessary. I know that cracked/cold solder joints is a common problem on Mac 128/512/Plus models but I don't think it's as widespread on the SE and SE/30. I don't think there would be an appreciable difference between brands in the chip you ordered, but I'll defer to those more experienced to chime in.

 

[Kai Robinson]

Sounds like we need to get @techknight onto this thread seeing as he's the person with all the CRT knowledge here!

 

[wskjinfen]

I speculate that this is likely a problem with the analog circuit, possibly due to a capacitor malfunction in the vertical scanning circuit. Some people also suggest checking if the deflection coil is loose.

 

[techknight]

That looks like noise getting into the vertical deflection circuitry. The original IC failed for a reason, and I think you are witnessing why it failed.

The problem is going to be how to figure out the actual cause. Perhaps, you could use an oscilloscope to probe the vertical drive signal into that IC and make sure it looks good. If that looks ok, then inspect the output waveform/check the impedence of the yoke itself. Shorted turns in the yoke could do this.

 

[shieldwolf]

I speculate that this is likely a problem with the analog circuit, possibly due to a capacitor malfunction in the vertical scanning circuit. Some people also suggest checking if the deflection coil is loose.

Sorry for the delayed response. I poured over the schematics by apple and bomarc for the analog board. I only noticed one possible problem with my recapping. I replaced C15 with a polarized cap, oriented correctly according to the silkscreen and schematics for polarity, but didn't realize the original was non-polar as per the schematics. I haven't changed it it out yet for the foil cap I bought as an alternative; I have to find small enough heatshrink to run a wire to the second leg. It doesn't seem to be a problem right now, but the use of non-polar is likely a consideration of back emf from the coil.

The deflection coil (the big one on the CRT right?) doesn't feel loose against the CRT. I tried jiggling and twisting with just enough force to usually detect mechanical slop, but didn't find any.

I had the thought that there might be some skin effect HV leakage across some of my hot glue (I don't have any solastic, and my initial searches only showed unsealable types for commercial application like a caulking gun. Any recommendations for glue stick style or affordable resealable options are welcomed, along with any experience in intermittent use and storage of the commercial types.) I carefully cut away any that looked like it might bridge any legs of anything but still offer vibration resistance for the capacitors and connectors.

Upon these checks, I hooked everything up and tried again, there was no flickery lines this time, but I'm not yet sure if it is solved or just an intermittent issue.

 

[shieldwolf]

That looks like noise getting into the vertical deflection circuitry. The original IC failed for a reason, and I think you are witnessing why it failed.

The problem is going to be how to figure out the actual cause. Perhaps, you could use an oscilloscope to probe the vertical drive signal into that IC and make sure it looks good. If that looks ok, then inspect the output waveform/check the impedence of the yoke itself. Shorted turns in the yoke could do this.

I have a rigol ds1202 i got on clearance. I would love to take a look at the vertical drive input, but before I do (still new to scopes,) I should use a battery backup (in lieu of an isolation transformer) to power either the scope or the computer right? and a 1x-10x probe is fine right?

As for the coil impedance, can I use the scope for this, or a ohm reading from a multimeter, or do I need an lcr meter to check that? what value ranges should I expect?