SE/30 Analogue Board troubles.

[MidnightCommando]

My SE/30 is currently in the process of an overhaul and return to stock condition - this includes returning its original analogue board to it, instead of having used the SE's analogue board as a stop-gap.

I've replaced the SMPSU unit and it's functioning just fine - however the horizontal sweep is not.

I know this because there is a thin one-or-two-pixel-wide line down the center of my screen.

R19 isn't burnt or charred or out-of-tolerance, it reads as 221.4R - definitely within the 5% tolerance the design allows for.

I replaced some of the capacitors with higher-quality and higher-voltage ones - i'm not sure if this somehow did something or if I missed something.

Hence, I need a schematic of the analogue board with refdes corresponding to the component references on the silkscreen so I can know what's going on, preferably one with the different portions (rails, inverter, horizontal sweep, vertical sweep, etc.) marked clearly... Can anybody help?

Alternatively, anyone have any ideas?

EDIT The part numbers on the silkscreen are: 820-0206-C and 630-0147-F.

 

[Mac128]

Have you checked C15? Also the yoke Plug at P1 may be burned. Also, check and re-solder pin 4 of the P1 connector and check/re-solder the coil at L2. Pina also recommends vacuum-desoldering the coil at L3 and re-solder with the R19 repair, but presumably since yours checks out, there is no need to do any of that.

 

[MidnightCommando]

L2 - I'm not sure how I'd fix that if it were broken, but I think it's ok.

R19 is fine.

C15 is original, I have no way of testing it and no way of replacing it short of wrecking a known working board to donate the part.

I don't have one of those multimeters that can check capacitance/inductance - any other things that are critical to the horizontal sweep?

P1 does indeed have a scorch mark on the solder-side, as well as browned connection on the component side. What's to be done about this? Presumably something shorted or sparked... a design flaw? If I fix it, is there a preventative measure to ensure it doesn't happen again?

 

[Osgeld]

what is so special about c15 you cant order it? if your in the states goto digikey, and you can use the usps shipping (for everything except batteries which kinda hacked me off) cost like 2$, no wrecking anything

 

[MidnightCommando]

Osgeld: You're not helping.

I didn't say I couldn't order it. I can. And I'm not in the US, as you could see if you read my Location in my little sidebar thingy on the post. It's just that I have no way of doing so until at least next Thursday, and I would prefer to isolate the problem before then. If it is the capacitor, I'll take it off my working board and replace the one in the working board later with a new part. However, I would like to know what comprises the rest of the sweep circuit before resorting to this, in case the answer /is/ in my pile of parts.

 

[Mac128]

Without a multimeter, then you are shooting in the dark. Macs are notorious for showing no signs of damage on failed components. In fact Larry Pina, arguably one of the most knowledgeable repairmen of compact Macs (at least published), often recommends a complete board re-cap when the obvious trouble-spots don't resolve the problem.

You seem to be looking for an easy answer, when the reality is, there may not be one, especially without the proper tools. I have given you all the expert solutions to your particular problem. Not that there couldn't be another problem, but those are the "easy" answers.

Have you inspected the inside of the vinyl insulator for singe marks that might pinpoint a failed component?

As for L2, I told you how to fix it: re-solder it. In many cases a cracked solder joint it the only problem, and simply needs a re-flow. Other times, as I indicated on L3, Pina recommends a complete cleanout and fresh solder. And even if you don't see any damage on pin 4 of P1, or P1 itself, a reflow may similarly solve that problem.

Also, C15 is one of the most notorious causes or problems in all the compact Macs in need of replacement. Pina recommends replacing it even if you are not having problems with it.

Check this out http://68kmla.org/files/

Otherwise, try searching the forum, I'm certain someone has posted a link to the video board schematics at some point, or just bide your time until that person reads this and provides it again.

And I think Osgeld was being perfectly helpful. You just didn't provide all the details. And there are certainly electronics dealers in AU and you could certainly buy from the US if they didn't. Like osgeld, I rarely notice someone's location. Notice he didn't assume you were in the US, but suggested a location if you were. This is also helpful to others in the US who may be reading and have a similar problem in the future. We're a community here, where our problems and solutions benefit everyone both now and in the future.

 

[MidnightCommando]

I have a multimeter, it just doesn't have an inbuilt Cx/Lx test circuit. I implied the presence of one when I gave the reading of R19 as 221.4R

I will replace C15 and reflow L2 and L3, if it will help. I was sincerely hoping at least it wasn't the replacement caps I put in - It would be very black humour for ELNA caps to suddenly stop working :beige:

As I asked, it's certainly possible that P1 is the problem, but why do the scorch marks and burning occur? Is this an error in manufacture, or does high voltage somehow jump and arc across the board, or what?

Also, thanks to a Corgi friend saving me yet again, I found some high-res schematic scans that were encoded to gif89a, they're probably not /strictly/ legal to distribute but I'm going to redo them when this mess is sorted and the schematics might be handy to someone else.

They are for the Sony SMPSU and the SE/30 Analogue Board (the model I have).

Thanks for all the help, I'll get back to you guys in about an hour and a half when I can actually solder again (the house is still asleep).

 

[Osgeld]

since I am not helping ..., you dont even really need a lcr meter, you need a gigantic ass resistor, a stopwatch and some math to calculate the current health on most electrolytic models (its those little ceramic buggers that require a computers assistance, because there is no way a humon could react)

 

[Mac128]

Pina's solution for your problem, given that P1 is scorched, is to re-solder c15, p1, & L2. If that does not fix the problem replace C15, preferably with a 3.9 mfd NP HF 100 V 85 〬C , L2 may also have to be replaced. If the plating is burned off pin 4 of P1, you'll have to replace the connector. Once you re-flow the solder on everything (before replacing anything), try slapping the case on the side and see if your horizontal sweep snaps on. That's a good sign only the connector needs to be replaced. If the L2 is not fused (i.e. can't be removed), it should be OK. Possibly true for L3. But if all that doesn't change anything, start looking to replace C15, which is extremely hard to test accurately in-circuit. Also, Pina recommends that if a re-flow fails and you have a known good C15, L2 & L3, then you should vacuum de-solder all components and re-solder with fresh new solder.

Ain't this fun!

 

[MidnightCommando]

Osgeld, apologies. Tone is difficult to read on the internet and I misread you as being somewhat snarky.

I do remember some time ago being taught about measuring capacitance using a resistor and stop-clock, in fact this explains why there are now kits that basically just do LC measurement with an oscillator and microcontroller :\ I don't suppose you'd be kind enough to elaborate? I think I might be able to rig something suitable up if only I know what i'm actually meant to be doing :I

(Also, does the resistor need to be made of a mule, or will carbonfilm / wirewound work just as well? )

Mac128, ... the plating burned off? OK, i'm accepting that fix as being A Good Idea™ but ... what? How does that happen? (As I've asked...) What is the cause of the burning?

When I reflow I tend to desolder and resolder anyway - makes things a lot cleaner when you have 440°C in your fingertips, thankfully I tried the slapping technique, no dice.

Might have to "borrow" known good C15, L2, L3, and P1 from the good board I have, figure out which of the taken parts is dicky, and replace accordingly - it's still virgin as long as the same spec parts are used, right? *grin*

 

[Osgeld]

no need to apologize I often am snarky

no I cant help you right now as I am at work, but you can google around on the subject and there is a few leads about it on there, if you dont have any luck in a couple hours I would be glad to show you how to do it, but you still have to remove the cap

as far as what type of resistor, no it does not really really matter, if your going on its face value a el-cheapo 5% is going to throw in a certain degree of error, course you should be able to get an exact reading with your meter and just work it in to your math for a more accurate measurement (keeping in mind the cap is going to have a tolerance too, but you would know for sure if its way out of wack or not)

weather it is worth the hassle or not is up to you (obviously to me its not but I have a small electronics parts store in my spare bedroom, so its easy for me to say screw it and replace it with a new part)

 

[MidnightCommando]

Good thing my assortment of resistors are metal-film 1% then - I always test them before use anyhow, so I'll throw it into my maths.

I'll elect to wait for your return from work - I can use the C15 from my other board until I find out what's going on at least. If this C15 really is FUBAR as the evidence seems to imply, looks like a trip to Jaycar is in the works for this week coming

I'll be soldering in a few minutes anyhow so meh >_>

 

[Mac128]

the plating burned off? OK, i'm accepting that fix as being A Good Idea™ but ... what? How does that happen? (As I've asked...) What is the cause of the burning?

Better minds than I can answer that question, but presumably it has to do with the large high voltages which are traveling across that pin and related components. If the C15 fails, there's little to resist the full charge passing through, hence the need to replace the C15 with a higher rated part than Apple originally chose.

 

[MidnightCommando]

Well I've just replaced L2, L3, and C15 on the analogue board, so we'll see if this works

 

[MidnightCommando]

This just in: It works.

The original L2 and L3 are functional, so it was indeed C15. Thanks guys, you're the best. <3

Now the SE/30 I was rebuilding is shipshape, time to start installing its complement of software!

 

[Osgeld]

just for the sake of completeness and since you asked, I found a old Tesla coil thread that describes how to measure capacitance with a meter and a stopwatch (which is good cause now I dont have to write it lol)

http://www.pupman.com/listarchives/1998/April/msg00625.html

1) You can measure the RC time constant.
T=R*C

Where: T is the time in seconds required to charge to 63%

of the battery voltage, and

R is resistance in ohms, and

C is capacitance in farads.

Note that if you measure resistance in megohms, then the capacitance

will come out in microfarads.

Re-arrange the formula so that

C=T/R

charge your cap through a resistor, and note how long it takes the

voltage to build from 0 volts to 63% of the battery voltage.

Use the formula C=T/R to determine the capacitance.

The circuit might look like this:

    ----------- Switch ------ Resistor --------------------
    |                                        |            |
  Battery                                 capacitor      voltmeter
    |                                        |            |
    -------------------------------------------------------

Note that the meter used should have as high an impedance as possible

to avoid loading down the circuit. In most cases you would probably be

using a 10 Megohm DMM. You can increase the effective input impedance of

the meter by using an operational amplifier connected as a Buffer

in front of the meter. You can use an LF356 for this purpose.

Start with the switch open, and the voltmeter showing 0 volts (short out

the cap for a few seconds to discharge it. Then close the switch, start

your stopwatch, and wait till the voltmeter hits battery voltage x 0.63.

Sadly, this only works well for large capacitors like electrolytics,

because you can do the timing with a watch. But for small capacitors

such as are used in tesla coils, you need to use a storage oscilloscope

or electronic timer/counter to measure the time 'cause it will be in

milliseconds or even microseconds.

and grats!

 

[MidnightCommando]

Ok, one more slight problem.

A pixel to the left of the raster appears to be worth two to the right... that is to say as I go left individual pixels get fatter, so looking to the left the screen looks slightly overwide and looking to the right, the icons look compressed - I end up with something like

   ====================================================
|  |                                                    ||
|  |        Welcome   to  Macintosh.                    || 
|  |                                                    ||
|  |                                                    ||
   ====================================================

on startup, which is a little disconcerting. Anyone know what I'd be adjusting to fix this?

 

[Mac128]

You need to adjust your voltages then adjust the display parameters, centering, width and size. Start with the comprehensive guide I linked to above