Jump to content

SE/30 where to start on Dead Screen


Recommended Posts

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?

 

Link to post
Share on other sites

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).

Link to post
Share on other sites

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 by Daniël Oosterhuis
Link to post
Share on other sites

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

Link to post
Share on other sites

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. 

Link to post
Share on other sites
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 by techknight
Link to post
Share on other sites

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.

Link to post
Share on other sites
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! :)

Link to post
Share on other sites
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 :-).

Link to post
Share on other sites

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.

Link to post
Share on other sites

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.

 

Link to post
Share on other sites
  • 2 weeks later...

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.

 

 

Link to post
Share on other sites
  • 2 weeks later...

Board is re-capped (plus a trace repair to one I damage removing C2).  Scrubbed, IPA soaked and dried.

 

Unfortunately I am still looking at a horizontal line.  I know its board related as another board works fine in this chassis.  I am off to do some reading about UE8 as a potential cause and how I might go about diagnosing the problem.

 

IMG_1037.thumb.jpg.bfd3fb1e974c78df5a3d283d6da6c775.jpg

Link to post
Share on other sites
On 1/25/2021 at 3:39 PM, Bolle said:

You are missing VSYNC most probably caused by a bad counter at UF8.

UE8 is likely fine on your board.

 

So I am looking at the schematics.  UF8 looks like it feeds into UG6 pins 2-8 and the VSYNC comes out of UG6 pin 14 which then connects to the PIN 11 on the Logic Board socket:

 

So I can check continuity between the UF8 and UG6 connections and continuity between UG6 pin 14 and Pin 11 on the socket.

 

I don't have a scope (yet) - I guess if I did I could power the board and look at the signals on these lines.

 

Assuming I can prove continuity I guess my next best step is to replace UF8 or am I better just going there first? 

Link to post
Share on other sites

So I have some progress to report.  I checked all the continuity between UF8 -> UGC -> HSYNC Pin on the main board (Pin 11) and there is continuity everywhere there should be.

 

So I went ahead and replaced UF8 and I now have VSYNC.  The picture fills the screen but is garbage:
after_uf8.thumb.jpg.6ae85a92a752f8c64560b5913c6190dc.jpg
 

The machine still appears to startup, I get a chime and the display comes on but it distorted.

 

So I then decided to go ahead and replace UE8.  Again the machine boots and I now get a different pattern:

 

after_uf8_ue8.thumb.jpg.5a581c89a8d0e97261608e0829501175.jpg

 

Startup is pretty much the same as before:

 

I am not entirely sure where to go next.

  • I'll do some googling and hit the bibles and see if anything matches
  • I'll do some continuity tests around UE8 and see if anything is missing
  • I suspect the next step you guys will suggest in getting it running on a bench and putting a scope on it - I now have access to a scope but have little idea of how and what to probe at this stage (I also don't have my extension logic board cable yet.

 

Any help you guys can provide would be greatly appreciated.

Edited by cannfoddr
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...