Color Classic II (Takky-d): top half of CRT de-sync issue?

[armadillu]

Hi! Just got a Color Classic II from Japan (Buyee), that was sold as Junk / not working. On the listing pics you could tell it had been Takky'd; it had tons of external cards (video, tv, ethernet + modem) but it looked to be in pretty decent shape cosmetically... I was willing to give it a try, so I got it. Anyway, when it finally arrived, I didn't want to turn it on before inspecting. Its a Performa 6200, all the Takky steps seemed ok, but it didn't quite start. The hard drive seems dead. I recapped the analog board, and it does start now...

It boots well (no sound, but I'll get into that later) off a blueSCSI; I even installed 8.1 just to check the reported video resolution (which is indeed 640x480). But the CRT makes an unpleasant noise, and the top half of the image is sort of de-synced, no matter what I adjust. I tried all the pots at the back. The only things that seems to make a real difference is when I adjust the VideoGain all the way to the top (it goes quite crazy) but even if I drop the gain to almost invisible, the top remains off-sync. The bottom image quality looks quite decent otherwise, albeit a bit soft (I'm guessing bc of the 640 x 480). Shifting the image up/down, or shrinking vertically doesn't affect the issue either. The only thing I haven't played yet is the PP1 potentiometer, as it seems to have been super-glued by the previous owner, and I can't adjust it at all.

Any ideas? I really really hope its not the flyback...

PS: I recorded a video so you can hear the sound as well. You can also see me adjusting the VG, and the effect it has on the CRT.

Video1 Video2

 

[armadillu]

Well, after a whole afternoon trying out different things, we have success!
I think one of the biggest issues I found was a bent pin on the analog board connector... Other than that, I re-soldered everything around the flywheel, and also cleaned the crt neck connectors.

 

[pizzigri]

Just to ask, what was the price of the CC and the final price you paid after everything? Looking forward to get something from Buyee as well but cant get and idea how much more I pay over the obvious auction or Buy it now price.

 

[armadillu]

It was a Yahoo Japan auction. I won the auction at 125€, but 10 min before closing it was going for 50€ or so.
I paid about he same for shipping, and then an extra 50€ for EU import tax and 45€ for DHL paperwork administration (which I was quite upset about, as they basically fill up one form, and you used to be able to do it yourself for free). It was sent very well packed (the seller sent it like that), but you can request Buyee to re-pack it better (at a price) if its not looking too good (you can also request a picture, at a price). All in all its not too bad, but I feel DHL ended up getting paid 120€ + 45€ for the shipping which seems way too high for the service they provide (don't get me wrong, the service is good, but I had no other choice, and they I feel they are taking advantage of it).

 

[pizzigri]

Wow. So, 125, plus 120, plus 50 plus 45. That's 340.... ouch.

 

[armadillu]

This is the auction link, in case anyone is curious. https://buyee.jp/item/yahoo/auction/u1089726051

 

[armadillu]

After a couple of days, it seems like the Analog Board is acting up. It started with a few flashes here and there, and it now seems to alternate between two states "voltage" states, supplying more or less voltage to the CRT at seemingly random times. I can adjust the pots for one or the other to look great, but they randomly switch from one to another. It can stay for several minutes in one state, and then randomly it changes to the other state where it seems more voltage is supplied to the CRT. This leads to showing over-write and with weird geometry when the state is in "high voltagte" (if I adjust the pots for the lower voltage state) or dark and squeezed image when the pots are adjusted for the high voltage state but the CRT is supplied with low voltage.

I measures the wattage at the wall socket; while the CRT is in the "high voltage" state, the mac consumes ~73 watts, and it consumes around ~65 watts when in the lower state.

I've also looked through the thermal camera and I can see some of the resistors and diodes really get too toasty for comfort, around 160c just after a couple minutes of operation. These looked really toasty from the begginning, I wonder if U should change them, although they read ok (with the multimeter) when unpowered. I had to re-trace with wiring on the diodes, as the traces look really flimsy (sort of detached from the board) and they created a couple ohms of resistance when reading with the multimeter.

I re-soldered all the parts of the board, so I'm pretty sure its not a bad contact. It also doesn't seem to be heat related, in the sense that the mac can start (from cold) in either state (low or high voltage).

Any ideas on what would cause the random voltage supply alternation?