STe PSU repair (Mitsumi 68-4231A)

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Re: STe PSU repair (Mitsumi 68-4231A)

Postby MRAtari » Wed Jan 20, 2010 2:27 pm

does anyone know where you can get the SHARP PC 101 chip from for this PSU?

that's the white chip in the middle

also how do you test the 0.47uf / 250v capacitor? this is C101 and is the black box package in front of the fuse

thanks

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Re: STe PSU repair (Mitsumi 68-4231A)

Postby 1024MAK » Thu Jan 21, 2010 2:28 am

C101 (0.47uF / 250V) is there to help suppress mains spikes and reduce unwanted noise and interference (both into and out of the PSU). As long as it is not short circuit it will not stop the power supply from working. The most basic test is to unsolder it and then test on resistance with a meter. You should get a very brief low reading which quickly goes to a very high resistance reading. If your meter has a capacitance range, test it on this range. If not you could buy / beg / borrow a meter with a capacitance range or buy / beg / borrow a capacitance meter. However considering the cost of a replacement (less than £2), you could just replace it.

The PC101 could well be hard to find!
Have you tried searching the internet for it?
Later I will see if I have time to post some links to electronic part suppliers.
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Re: STe PSU repair (Mitsumi 68-4231A)

Postby MRAtari » Thu Jan 21, 2010 11:20 am

1024MAK wrote:C101 (0.47uF / 250V) is there to help suppress mains spikes and reduce unwanted noise and interference (both into and out of the PSU). As long as it is not short circuit it will not stop the power supply from working. The most basic test is to unsolder it and then test on resistance with a meter. You should get a very brief low reading which quickly goes to a very high resistance reading. If your meter has a capacitance range, test it on this range. If not you could buy / beg / borrow a meter with a capacitance range or buy / beg / borrow a capacitance meter. However considering the cost of a replacement (less than £2), you could just replace it.

The PC101 could well be hard to find!
Have you tried searching the internet for it?
Later I will see if I have time to post some links to electronic part suppliers.


thanks

i'm going to get a capacitance meter as it seems the obvious and easiest option

as for PC 101 yes i've looked and found nothing so far, possible a compatible replacement could be out there but i know nothing about these things so if you know of any such comparible parts that would be appreciated :)

also do you know if the original bridge rectifier is 1.5amp?

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Re: STe PSU repair (Mitsumi 68-4231A)

Postby Hippy Dave » Thu Jan 21, 2010 9:49 pm

There is no pin-for-pin replacement part for the Sharp PC101.
I just noticed that the Optek OPI1264A has much less collector
current capability, So I am withdrawing it as a replacement.

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Re: STe PSU repair (Mitsumi 68-4231A)

Postby MRAtari » Thu Jan 21, 2010 10:30 pm

is the Optek OPI1264B any good?

i can get those......

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Re: STe PSU repair (Mitsumi 68-4231A)

Postby Hippy Dave » Thu Jan 21, 2010 11:17 pm

***Amendment***
Use a CNY65 (see further postings)
********************
The problem with the OPI1264A and OPI1264B is the maximum collector
current is 5.95 mA, the PC101 is rated at 50 mA, and the schematic looks
like 5.95 mA won't cut it.

A Fairchild CNY17F1M looks good.
Maybe the easiest solution is to break the unused pins off of the new
opto-isolator, bend the remaining pins outwards and solder extension
wires between them and the pcb holes. The new opto will be mounted
in the same spot as the PC101, but rotated 90 degrees with pin 1
closest to the isolated secondary side.

Matching pins CNY17F1M vs PC101 are:

1 == 7
2 == 8
3 unused
4 == 13
5 == 2
6 unused

Note that the black dot on the PC101 is to mark the anode, it is Not
pin 1 (it is actually pin 7). The beveled edge designates that pin 1
is to the top left when looking at the IC from the top with the
beveled edge to the left (in this case). On the CNY17F1M, pin 1 is
designated by a dot (and pin 1 happens to be the anode also).
Last edited by Hippy Dave on Fri Jan 22, 2010 10:20 pm, edited 1 time in total.

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Re: STe PSU repair (Mitsumi 68-4231A)

Postby MRAtari » Fri Jan 22, 2010 12:06 pm

also i did wonder would the CNY 65 from an Atari PSU work too? it should as i once saw a PC 101 used in an Atari PSU!

the pins actually line up to!

just thought too, the DSP 508A PSU has a CNY17-3 which looks similar to the one you mention above, would this work? as i have some of those and they are very cheap and easy to get too

thanks for your help Dave :)
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Re: STe PSU repair (Mitsumi 68-4231A)

Postby Hippy Dave » Fri Jan 22, 2010 10:09 pm

MRAtari wrote:also i did wonder would the CNY 65 from an Atari PSU work too? it should as i once saw a PC 101 used in an Atari PSU!

the pins actually line up to!

just thought too, the DSP 508A PSU has a CNY17-3 which looks similar to the one you mention above, would this work? as i have some of those and they are very cheap and easy to get too

thanks for your help Dave :)

The CNY65 looks like the part to use!
The pin 1 'ic reference mark' goes towards the isolated
secondary side of the circuit.
Note that pins E and C (emitter and collector) will go
into two unused holes on the Mitsumi 68-4231A pcb
(because the pin spacing is 0.6", and 0.5" is needed).

The CNY17-3 could be used in place of the CNY17F1M in
this case. (the CNY17F1M cannot replace a CNY17-3)

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Re: STe PSU repair (Mitsumi 68-4231A)

Postby MRAtari » Wed Feb 17, 2010 5:53 pm

cool

well i've used CNY 65 in place of PC 101 and it works fine! :)

looking at the spec sheets CNY 65 is a better part anyway

so if anyone else is looking to replace PC 101 use a CNY 65 (same as found in the original Atari PSU) as they are easy and cheap to find, PC 101 is long gone as i have found....

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Re: STe PSU repair (Mitsumi 68-4231A)

Postby Inks » Fri Apr 02, 2010 12:41 am

Hello again. Have finally gotten 'round to more testing etc. Thought I should post and ask a couple more things.

All caps (except C101) and the bridge rectifier are now replaced, along with the Zener that originally blew. Power supply still doesn't start up.

Next suspects, having read the posts above, are D201, Q101, Q102 and the resistors... I will be testing these soon, I'm just waiting on a desolder pump through the post as it was cheap enough and I figured it'd beat the copper braid I've been using so far.

I'm considering just replacing all the small resistors (Carbon Film 0.6W, I'm guessing?) on the board anyway- they're fairly cheap and the ones on there are old. Good idea? If so, is it OK to replace the Carbon Film resistors on there with equivalently rated Metal Film ones? I don't think this would matter much, but it would be good to have some input from someone who actually knows. :)

Also, where's the best place to source these various components in the UK? I've been buying from Maplins, but there's no way they're going to have a CNY65 in stock...

Cheers.

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Re: STe PSU repair (Mitsumi 68-4231A)

Postby MRAtari » Fri Apr 02, 2010 11:35 am

if Q1 has gone then so will Q2 and PC101, they almost always blow together - and yes as i said above the CNY 65 is a perfect replacement but you'll have to do some modding, ie: link 2 of the pins back to the solder pads under the PCB

also check R101 which is the white square resistor next to the big main cap (or in your case under the replacement one)

also check R103 i think, it's a 3.3 OHM grey resistor again i can see it's under the big cap you have laying down, these usually go along with Q1 and Q2 etc

if they have all gone then you need to change them all as a set

if you can't get the parts from maplin craplin then try ebay if you just need 1 offs, i know CNY 65's are on there and Q1's and Q2's

mind you after you've bought all the parts you probably could've bought another power supply for the same money!

if you get stuck and need one i can sought you out with a nice refurbed one :)

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Re: STe PSU repair (Mitsumi 68-4231A)

Postby 1024MAK » Fri Apr 02, 2010 3:07 pm

Metal Film resistors are fine (and better than carbon film).
Resistors that have a high voltage across them can die due to age, most resistors in the rest of the circuit do not get stressed unless something else dies (like one or both transistors).
Always test the resistance of the existing resistors (you may have to desolder one end if other parts of the circuit affect the reading).
Also measure the resistance of any replacement resistors. It is easy for both your supplier or yourself to "see" the wrong colour on the body - I have both made a mistake myself and so has one of the companies that I bought parts from.

If you cannot find the parts you need on ebay, try the main electronic component suppliers.

Some of the big companies that supply the UK market are
Rapid Electronics Limited, Severalls Lane, Colchester, Essex C04 5JS United Kingdom http://www.rapidonline.com/
Premier Farnell UK Limited http://uk.farnell.com/ and http://www.farnell.com/
RS Components Ltd. Birchington Road, Corby, Northants, NN17 9RS, UK http://uk.rs-online.com/web/ and http://www.rs-components.com/index.html
Also ESR Electronic Components Ltd - 0845 251 4363, http://www.esr.co.uk.

I have used all of the above companies. You do not have to be a business, they will sell to individuals (they take credit card orders over the phone). The only thing to watch for is the postage / packing / shipping / small order charges.

There are also some smaller firms, but they have a more limited range. Some of them can however help with sourcing components.
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Re: STe PSU repair (Mitsumi 68-4231A)

Postby 1024MAK » Fri Apr 02, 2010 3:15 pm

The first resistors to check (and or replace) are any that are greater than 100k Ohms or less than 47 Ohms in value.
Going on that Hippy Dave thinks that R102 is the start up resistor, I would go for this one first. Use a resistor that is rated at 500V if you can get your hands on one. If not try a 250V one for testing and replace it as soon as you can. If there is space, higher wattage resistors can last longer.
R102 (I can't see it, I'll guess it is about 330K ohms) is the closest thing to a start-up resistor here (runs too).
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Re: STe PSU repair (Mitsumi 68-4231A)

Postby gibs » Sun Apr 03, 2011 6:22 pm

Hi guyz.
I found this thread coz I was looking for a schematic for the Mitsumi 68-4231.
I'm also trying to fix this PSU.
http://www.youtube.com/watch?v=PxnBwk5HcZo

After changing all the 6 electrolytic caps, the PSU has worked 1 time. Then back to low voltage.
I let the psu plugged for 5 minutes to see how it evolve and something burnt (I head "pscchhhtt") and the voltages were down to 0V.

I have almost unsoldered 1 leg of each resistors & diode from the board, now I need to check them.
I found that R106 is dead (infinite value). It's supposed to be a 3,3 ohm resistor.

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Re: STe PSU repair (Mitsumi 68-4231A)

Postby gibs » Sun Apr 03, 2011 6:22 pm

Hi guyz.
I found this thread coz I was looking for a schematic for the Mitsumi 68-4231.
I'm also trying to fix this PSU.
http://www.youtube.com/watch?v=PxnBwk5HcZo

After changing all the 6 electrolytic caps, the PSU has worked 1 time. Then back to low voltage.
I let the psu plugged for 5 minutes to see how it evolve and something burnt (I head "pscchhhtt") and the voltages were down to 0V.

I have almost unsoldered 1 leg of each resistors & diode from the board, now I need to check them.
I found that R106 is dead (infinite value). It's supposed to be a 3,3 ohm resistor.

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Re: STe PSU repair (Mitsumi 68-4231A)

Postby 1024MAK » Fri Apr 08, 2011 2:42 pm

Hmm, 5.5V on the 5V output is a little bit high :( (info from the video)
I know some people like a slightly high 5V rail, but most "TTL" logic chips are rated for 5V +/- 5% giving 5.25V as the highest normal supply voltage.
I assume that you did not adjust VR201? Adjusting this varies the output voltage on the regulated +5V supply. But if all you changed was the capacitors, this should not have needed adjusting.
As R106 needs replacing then I would also renew Q101 and Q102.
I suggest you replace the opto-coupler PC101 as described in the posts above. Use a CNY65. It would also be a good idea to renew IC201 – TL431 (or TL431C)
Ensure that R101, R102, R103, R201, R203 have also been checked and tested.
Note that after doing all this you may need to adjust VR201.
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Re: STe PSU repair (Mitsumi 68-4231A)

Postby sadmanx » Thu Jul 21, 2011 9:46 pm

hi guys, great thread, i'm just trying to repair the same psu

so far i've found R101 and R106 to be dead, i'm wonderng, if any of those transistors (Q101 and Q102) are dead too, are there any suitable replacements or i have to ebay the same ones?

(Q101 - 2SC2979, Q102 - 2SC2060)

thanks

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Re: STe PSU repair (Mitsumi 68-4231A)

Postby MRAtari » Sun Jul 24, 2011 4:41 pm

if R101 and R106 are dead then Q1 / Q2 and PC 101 will be dead too

repaired loads of these and it was always those parts go together

if you don't replace PC 101 and do replace the others you will blow all the new parts again! so replace those 5 parts

i used a CNY65 in place of the PC 101 you just have to fit it in with the writing upside down compared to the original PC 101

you can't get PC 101 but CNY65 are easy

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Re: STe PSU repair (Mitsumi 68-4231A)

Postby sadmanx » Sun Jul 24, 2011 5:45 pm

MRAtari wrote:if R101 and R106 are dead then Q1 / Q2 and PC 101 will be dead too

repaired loads of these and it was always those parts go together

if you don't replace PC 101 and do replace the others you will blow all the new parts again! so replace those 5 parts

i used a CNY65 in place of the PC 101 you just have to fit it in with the writing upside down compared to the original PC 101

you can't get PC 101 but CNY65 are easy

took a few days for my post to get approved, i got further meanwhile

so besides R101 and R106, i found bad R114, D105, Q101, Q102

no idea what D105 was originally, i've replaced it with 1n4148
transistors were replaced by BUT11A and BC337 (different pinout)
didn't test pc101, replaced it with CNY65, same for voltage reference
changed all electrolytic caps

it seems to work now although i haven't tested it with full load yet (that 1040stfm it came from is broken too), just around 400ma on 5v

any comments on these replacements before i try it on full load?

thanks

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Re: STe PSU repair (Mitsumi 68-4231A)

Postby MRAtari » Sun Jul 24, 2011 8:29 pm

never seen R114 or D105 go but hey if you replace them with the same or compatible parts then ok

test it under load formatting a disk and adjust the 5v pot to get it at 5v

then let it run for 30 mins or so

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Re: STe PSU repair (Mitsumi 68-4231A)

Postby sadmanx » Sun Jul 24, 2011 11:07 pm

MRAtari wrote:never seen R114 or D105 go but hey if you replace them with the same or compatible parts then ok

test it under load formatting a disk and adjust the 5v pot to get it at 5v

then let it run for 30 mins or so

long way there, i need to fix the machine first
just desoldered 4 ram chips that were heating like mad and drawing around 1A extra which might have killed the psu

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Re: STe PSU repair (Mitsumi 68-4231A)

Postby radu14m » Sun Apr 29, 2012 10:52 am

Hi together,

I am very new ( greenhorn ) in this area, let say Atari area.
Just grow up using z80 maschines and from couple a days i get an atari 1040stfm witch capture my heart :)
Unfortunately, the PSU died yesterday.
I simply turn the atari off, and when i turned it on agin the 1Amp fuse blow ( with a flash ).
Then i replace it, thinking that it was voltage spike or something like this.
Unfortunately this didn"t help, the fuse blow again with a flash :(

Everything on the board looks ok, no burn parts, no bulb caps....
I need your help getting my baby back :)

Thanks a lot !

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Re: STe PSU repair (Mitsumi 68-4231A)

Postby radu14m » Tue May 01, 2012 12:37 pm

on my PSU the fuse ( 1 A / 250 ) blows with a flash.
I replaced it, but it burns again.

Any ideea what could lead to this ?
What should i check in the PSU ?
:roll:

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Re: STe PSU repair (Mitsumi 68-4231A)

Postby Jorevall » Tue Feb 25, 2014 1:21 pm

This tread might be old..
I'm having an issue with a PSU, I do have +5 and +12, but when loaded via a 1040STe, the voltage drops, I have maximized the pot för the opto part..
Switched PSU have never been fun to repair, but does anybody have a clue where to look?

I have checked all the caps, and only the 1u/50 inte opto part had a low value, but that did not change anything..

Thanks in advance..

( I tried a spare falcon psu, and that was dead on +5v while loaded in the STe.. )

Regards,
Freddie
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Re: STe PSU repair (Mitsumi 68-4231A)

Postby exxos » Tue Feb 25, 2014 1:41 pm

Jorevall wrote:This tread might be old..
I'm having an issue with a PSU, I do have +5 and +12, but when loaded via a 1040STe, the voltage drops, I have maximized the pot för the opto part..
Switched PSU have never been fun to repair, but does anybody have a clue where to look?

I have checked all the caps, and only the 1u/50 inte opto part had a low value, but that did not change anything..

Thanks in advance..

( I tried a spare falcon psu, and that was dead on +5v while loaded in the STe.. )

Regards,
Freddie


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