Recapped SE/30 with No Video

[MeTheMac]

Hi,
I got a recapped Macintosh SE/30 and the motherboard needed some work so I sent it off to u/AmigaOfRochester to get it all fixed up -- great guy, he did fantastic work on the SE/30 motherboard and my Mac Portable motherboard, highly reccommend! At the time of purchase the machine powered on and went to the desktop but had a few issues, like no sound.

However, I just got it back and plugged everything in and for some reason the CRT doesn't seem to be outputting any video! I've tried changing the wheel on the front of the Macintosh and the Cut Off pot but no luck.

The board on the back of the CRT is plugged in and I have reflowed the Analog board connectors. I don't see any light or anything in the glass at the back of the tube when powered on if that is important. The Fan does spin up.

Thank you!

(repost from r/VintageApple Reddit post)

 

[vtgearhead]

I can't tell from the available diagrams, but some video displays powered the CRT filament from a winding on the flyback transformer. If that's the case with the SE/30 then missing H-Sync from the motherboard would result in the symptoms you describe.

 

[MeTheMac]

@vtgearhead What would that mean? How could I fix it?

 

[vtgearhead]

It could mean just about anything (motherboard, cabling, something on the analog board), but first step is to find out if heater voltage in the SE/30 is tapped off the flyback. I took a quick glance at the available diagrams and it's really not clear how the heater is powered.

 

[MeTheMac]

Hmm, okay. Sorry for my inexperience but how would I test the heater voltage? Tysm for the help!

 

[vtgearhead]

Please don't take this the wrong way, but if your bench skills are limited it's much healthier (in the physical sense) to not poke around in the display electronics. Beside the second anode lead from the flyback to the tube, there are high voltages on the analog PCB.

 

[MeTheMac]

Totally understand. I'm pretty new to CRTs but I'd really like to try to fix this if possible.

 

[JDW]

@MeTheMac
You did not mention if you hear a bong when you power on. You only said the screen is dark. A bong would be a sign of life.

Next, because Amiga of Rochester did the repair, it would be good to ask him his advice in light of your current symptoms. Do that just to make sure he didn't overlook something during his repair.

Next, I suggest you start with page 147 in Larry Pina's Dead Mac Scrolls book to see what symptoms may match what he describes there:

The Dead Mac Scrolls 1992 : Free Download, Borrow, and Streaming : Internet Archive

The Dead Mac Scrolls 1992

archive.org

 

[MeTheMac]

Haha, completely forgot. Yes, chime is present. I have reached out to Amiga of Rochester and we are led to believe their is something wrong with my CRT or Analog board of the system, but not sure where to continue from there.

 

[JDW]

It's at times like this that having more than one model of the same Mac is very handy. If you only had another SE/30 or SE, you could put your motherboard in that other machine and test it. If all is well, then you could do an Analog board swap. If all is well, then you could know if indeed the CRT is bad (however unlikely that is).

 

[MeTheMac]

Haha, yeah. I'm getting an LCD and new PSU soon so hopefully I can install that, just trying to eliminate as many issues before I install it, but I guess we'll see!

 

[robin-fo]

Haha, yeah. I'm getting an LCD and new PSU soon so hopefully I can install that, just trying to eliminate as many issues before I install it, but I guess we'll see!

Your analog board is certainly repairable; if you decide to part with it and the CRT, please consider offering it for sale here!

 

[MeTheMac]

I definitely will be!

 

[djc6]

I like using a device like this to easily see if there is HSYNC or VSYNC signal at the J12 connector (I don't own this):

SE-COMBO (IDC12) - Joe's Computer Museum

The SE-COMBO brings together features of two of our best sellers; the Universal TTL Video Adapter and the ATX Breakout Adapter.

jcm-1.com

There is also a similar device that outputs VGA - bypassing the analog board: https://jcm-1.com/product/se-combo-macpicovid-edition/

You can also power SE/30 off ATX power supply for bench testing just the logic board.

Here is a thread with more info and videos showing how to use these devices: https://tinkerdifferent.com/threads...uality-video-output-on-your-compact-mac.3890/

I don't own either of the above devices, they didn't exist at the time I bought more expensive device from CayMac vintage that outputs HDMI instead of VGA:

https://ko-fi.com/s/e600bd3867

This has been super helpful for bench testing my SE/30 and connecting a much larger LCD to the system. But I'm intrigued by the much cheaper options from Ron's Computer Videos.

I had recapped an SE/30, it ran for a few hours great - and then no video. Chip "UG8" failed which prevented both HSYNC and VSYNC from being generated. It had been damaged by leaking electrolyte. The system would give a happy chime on startup.