SE/30 where to start on Dead Screen

[cannfoddr]

Very new to this so please be gentle.  

 

I've picked up a SE/30 which chimes on power on and has hard disk activity but the CRT shows no sign of life.  I have read through the documentation that I can find and I am pretty certain I am looking at some sort of analog board problem.  There is a lot of blackish residue across the inside top of the case, the fans and the top of the CRT.  The flyback cable has sticky residue at both ends.  I have visually inspected the back of the analog board and It looks pretty clean with no obvious issues.

 

Not sure where to go next to try and narrow down the problem?

 

[cannfoddr]

Just found this https://www.jagshouse.com/classicrepair.html - 5.2 looks like a good match:

 

5. Monitor Black Out with/without Startup

Symptoms
As to the symptoms when turning on the power, there are four types including
(1) Black monitor with startup bong;
(2) Black monitor with startup bong and with spining sound of fan and hard disk drive;
(3) Black monitor without startup bong but with click noise; and
(4) Black monitor without startup bong and without click noise.

Diagnosis
The most probable cause of this trouble is damage of the CR2/CR3 rectifiers or the Q2 transistor.
Troubles of the T2 flyback transformer sometimes results in this problem.
The broken CR5 rectifier also causes these symptoms, though rarely.
CR2 and Q2 are placed on the outer surface of the metal cage, which shields the flyback transformer on the analog board. The cage metal around CR2 and Q2 is locally discolored/charred, or these parts are exploded by high temperature.
If the CR3 rectifier is damaged by heat, explosion of CR3 usually occurs. CR3 is placed on the inner surface of the shielding metal cage.
When CR3 is damaged but not exploded, the Q2 transistor may be damaged simultaneously. In this case, Q2 is sometimes burnt and sometimes is not.
When Q2 is burnt out but CR3 seems to be OK, the CR5 rectifier is probably damaged.
Even if all CR2, CR3, CR5 and Q2 appear to be OK, the inner circuits of these parts are sometimes destroyed by heat.

Even if all these semiconductors are OK, destruction of the R22 resistor also can cause Symptom(2) as described above (Black monitor with startup bong and with spining sound...).

Solutions
Replace the broken semiconductor or resistor with new one.
CR2 and CR3 (silicon rectifying diode): GI854 (600V,3A). The much better is MR824 (600V, 5A).
CR5 (silicon rectifying diode): 1N4937 (600V, 1A).
Q2 (NPN transistor): BU406 or BU406D (7A, 60W). If you cannot get BU406/BU406D, use RCA SK9085.
R22 (resistor): 470 Kohm, 1/2 W, 5%.

When the SE/30 appears totally dead (black out monitor, no startup bong, no spinning sound, no noise), the major cause of the problems is the power supply (SONY or ASTEC). Check the power supply/power switch with a digital multimeter. If the power supply doesn't work, replace it with another one (new or used).

[Daniël Oosterhuis]

Before jumping to the analog board, has the logic board been recapped? Has it been inspected for potential damage from cap leakage? Traces can be damaged, as well as some of the 74 logic chips which are part of the video generation circuitry. Is the CRT totally off, or does turning up the brightness show you some sign that it's on? These old guides are going off problems owners might have faced back in the day, when the caps weren't leaking yet. All, and I mean all SE/30s need to be recapped, and no video is a sign of cap leakage related failure.

Edited December 23, 2020 by Daniël Oosterhuis

[bibilit]

I will have a look at bad solder joint first, common issue on Pluses but also seen on SEs. 

 

Connector J1 IIRC

[cannfoddr]

The Logic board has NOT been recapped.  Its on my list of things to do.  However i have inspected the board and they seem to be in surprising good condition.  I found a battery with 10-89 coded on it which could be the manufacturing year!!!  

 

Some Photos attached - I know it needs doing but I don't think its root cause here.

 

Brightness control seems to make no difference to the display there is nothing.

 

Should I be prioritising logic board recap over the lack of display?

 

IMG_0921.HEIC IMG_0922.HEIC IMG_0923.HEIC IMG_0924.HEIC

[cannfoddr]

sorry about the heic files - there is a windows extension here: https://www.microsoft.com/en-gb/p/heif-image-extensions/9pmmsr1cgpwg?activetab=pivot:overviewtab

 

[dochilli]

Try to reseat the neck board on the crt. Check the solder joints on the neck board.

[cannfoddr]

So it turns out the CRT is not dead - thanks for all the pointers here.  I adjusted the cutoff and re-soldered J1 C15 and L1 and I have signs of life - I now have a horizontal line.

 

I've read the docs on this one and have continuity checked J4 through to the logic board connector - that's OK.

 

Not sure where to go next but I plan to do some more reading around and see what I can come up with. 

[techknight]

as I mentioned in your other thread (Just now found this one, sorry). 

 

you need to recap and clean the logic board before you can do anything. Black screen is a known symptom of this, as well as a potentially bad LS166. 

[techknight]

4 hours ago, cannfoddr said:

So it turns out the CRT is not dead - thanks for all the pointers here.  I adjusted the cutoff and re-soldered J1 C15 and L1 and I have signs of life - I now have a horizontal line.

 

I've read the docs on this one and have continuity checked J4 through to the logic board connector - that's OK.

 

Not sure where to go next but I plan to do some more reading around and see what I can come up with. 

 

Also, You should attempt to resolder ALL the connections on the analog board. You also need to check the horizontal and vertical drive signals from the logic board with a scope, along with the video signal, If the line runs up and down, then you need to fix the yoke connections on the analog board, and potentially ohm out and test the yoke itself. 

 

most of the time the cap near the LS166 and the LS166 chip itself goes bad and keeps the video signal in the cutoff range. therefore, black screen. 

Edited December 30, 2020 by techknight

[cannfoddr]

I don't have access to a scope.  

 

I'll start with the recap.  For cleaning what's the best approach in the absence of an ultrasonic cleaner?  I have access to IPA and swabs and a toothbrush.  I've read comments about using a dishwasher but that sounds scary!  I've looked at cheap 10L ultrasonics on Amazon but I am uncertain.

[davidg5678]

2 hours ago, cannfoddr said:

 I have access to IPA and swabs and a toothbrush.

These should be adequate. There are a lot of toxic chemicals on these circuit boards (including lead), so putting them into a dishwasher that cleans things you eat off of doesn't seem like a good idea to me. A lot of people swear by this technique, but it doesn't seem very healthy to me.

 

You probably can fix this board without using an oscilloscope. Most of the time, cleaning the logic board with Isopropyl alcohol and replacing the capacitors fixes things. The analog board and power supply may also need new capacitors, but it is best to start with the logic board. I agree that re-flowing all of the solder joints on the analog board would be helpful for troubleshooting, and it shouldn't take too long either.

 

I would recommend recapping everything (logic board, analog board, and power supply) and seeing where that gets you. It is possible that something else is also broken, but recapping each of these boards is something that needs to be done regardless of any other faults.

 

Good luck!

[cheesestraws]

16 hours ago, cannfoddr said:

I have access to IPA and swabs and a toothbrush.

 

This, plus an old washing up bowl, is what I use.  I have occasionally thought about getting an ultrasonic cleaner but I haven't actually had a board that needed one yet, nor do I have the space for it, so a toothbrush and IPA will do .

[joshc]

Yes to IPA and swabs, and ideally an anti-static brush but a toothbrush tends to be OK too. I tend to do an IPA soak as well after scrubbing and then leave to dry fully for a couple of days, and then hit it with hot air/compressed air to make sure it's completely dry.

[cannfoddr]

So after 2 days of messing with this thing I have decided to give up and turn it into a fish tank of something....

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ok calm down I am, of course, joking

 

I just did what I should probably done in the first place and dug out my EXISTING Mac SE/30 and tried some strategic swapping of components between the two.  

• The NEW mac with the EXISTING logic board - works fine (Existing logic board has no sound issue and is awaiting its recap)
• The EXISTING mac with the NEW logic Board exhibits the same lack of vertical scanning seen on the original

As pointed out by others the problem seems to be the logic board - I need to start with a recap on this NEW board.  I seem to recall UE8 is the main culprit for video problems I will do some research whilst I am waiting for Mouser to deliver my 2 sets of Logic Board and Analog Caps.

 

[Chopsticks]

yes I would check UE8 and the traces that connect to it as the first point of call, also download the se/30 schematics and trace out the connections. but before you even do that recap the logic board and give it a very, very good clean

[cannfoddr]

Am in the process of doing the recap but I broke a trace (see my recap post).  Have the wire for a repair but waiting for Amazon to deliver some solder mask, am going to practice my trace repair on a prototype board from another project before I move on to the mac logic board.

 

Washing up bowl, IPA, and anti static brushes are standing by for the clean and soak.