View Profile: Hugo Holden - Vintage Computer Forum

Today, 02:07 PM

Hugo Holden replied to a thread Has anyone else encountered the inexplicable wrong-size stuck screw? in Vintage Computer Hardware

In my restorations of vintage equipment I often use stainless screws. The main supplier of small sized stainless screws in the USA is PSME ...

13 replies | 96 view(s)

Yesterday, 01:43 PM

Hugo Holden replied to a thread MAcintosh Classic CRT Inside Apple IIc monitor in Early Apple (I, ][, ///, etc.)

I didn't document it, but it would have been one of two CRT's. Looking at the Apple IIc schematic, the CRT there is a C10M42P31, and I must have...

4 replies | 143 view(s)

March 2nd, 2021, 01:22 PM

Hugo Holden replied to a thread Help! looking for a low cost low profile pin header. in Vintage Computer Hardware

Those might suit a dual wipe socket which are more forgiving on slightly oversized flat pins, but it would pay to know the exact measurements,...

8 replies | 180 view(s)

March 1st, 2021, 06:52 PM

Hugo Holden replied to a thread MAcintosh Classic CRT Inside Apple IIc monitor in Early Apple (I, ][, ///, etc.)

If the CRT's you propose to swap have essentially the same part number, but say P31 for green and P4 white, or their part numbers indicate they are...

4 replies | 143 view(s)

February 28th, 2021, 09:22 PM

Hugo Holden replied to a thread Help diagnosing a 1084S-P Monitor in Vintage Computer Hardware

The puzzling thing is how the flyback voltage can look so good, especially in light of the 125V being reduced to 60V. And how it could be that the...

19 replies | 257 view(s)

February 28th, 2021, 02:46 PM

Hugo Holden replied to a thread Commodore 1541 5.25" disk drive question. in Commodore

Hi Mike, I have not received the AH5050 yet, it is still in the slow post, but I have the Commodore disk drive & cable. Thank you for the...

11 replies | 247 view(s)

February 28th, 2021, 01:42 PM

Hugo Holden replied to a thread Help diagnosing a 1084S-P Monitor in Vintage Computer Hardware

The zero LED current proves that the supply is running flat out, so it is overloaded, the negative feedback is not operating. Just checking, the...

19 replies | 257 view(s)

February 28th, 2021, 06:30 AM

Hugo Holden replied to a thread Help diagnosing a 1084S-P Monitor in Vintage Computer Hardware

Its possible, check for damaged components on the neck board. If the supply output voltage had dropped due to current overload, one would expect...

19 replies | 257 view(s)

February 28th, 2021, 02:26 AM

Hugo Holden replied to a thread Help diagnosing a 1084S-P Monitor in Vintage Computer Hardware

Yes, I agree it should be zero, unless say it was being cyclically triggered and the SCR coming in and out of conduction, and what we are seeing is...

19 replies | 257 view(s)

February 27th, 2021, 09:47 PM

Hugo Holden replied to a thread Help diagnosing a 1084S-P Monitor in Vintage Computer Hardware

I have developed a theory on what could be wrong, since these is no actual current sensing of the power supply output, the only way the supply...

19 replies | 257 view(s)

February 27th, 2021, 07:45 PM

Hugo Holden replied to a thread Help diagnosing a 1084S-P Monitor in Vintage Computer Hardware

One possibility, it could be a situation where the power supply is just being pushed into a shutdown or protected mode, when its 125v output drops to...

19 replies | 257 view(s)

February 27th, 2021, 07:12 PM

Hugo Holden replied to a thread Help diagnosing a 1084S-P Monitor in Vintage Computer Hardware

Ok, To summarize: It is not something on the -21V rail loading it. We are left with a situation where, apparently the H output stage is drawing...

19 replies | 257 view(s)

February 27th, 2021, 06:18 PM

Hugo Holden replied to a thread Help diagnosing a 1084S-P Monitor in Vintage Computer Hardware

I think the HOT drive waveform is probably ok, the transistor is switched on for about the correct time period and the frequency is close enough. ...

19 replies | 257 view(s)

February 27th, 2021, 03:23 PM

Hugo Holden replied to a thread "New" oscilloscope. Very exciting. in Vintage Computer Tools

One interesting thing about a CRT based scope, especially Tek, right up to the time that CRT's became obsolete, the technology was perfected after...

7 replies | 185 view(s)

February 27th, 2021, 02:48 PM

Hugo Holden replied to a thread Commodore 1541 5.25" disk drive question. in Commodore

Hi Mike, I just bought a Zoomfloppy, it should help me. With that remark about running BASIC, do you mean trying to run a separate BASIC from...

11 replies | 247 view(s)

February 26th, 2021, 06:24 PM

Hugo Holden replied to a thread Help! looking for a low cost low profile pin header. in Vintage Computer Hardware

The header, if it has round pins, the pins must have a diameter of 0.45 to 0.5mm. This is the size that suits a round machine pin IC socket, without...

8 replies | 180 view(s)

February 26th, 2021, 12:19 AM

Hugo Holden replied to a thread Fixing Broken Mechanical Switch Key Stem On Nakajima Printer? in Vintage Computer Hardware

These sorts of plastics are super resistant, like Nylon, to any form of chemical adhesive. If I were fixing that I would find a way to clamp both...

6 replies | 147 view(s)

February 25th, 2021, 07:21 PM

Hugo Holden replied to a thread Help diagnosing a 1084S-P Monitor in Vintage Computer Hardware

Looking at the the screen image at the moment of the major failure the H scan is collapsing and looking prior to that the H scan amplitude was...

19 replies | 257 view(s)

February 25th, 2021, 01:44 PM

Hugo Holden replied to a thread Commodore 1541 5.25" disk drive question. in Commodore

I'm hoping I will be able to get this to run with my AIM-65 with the AH5050 adapter board. Apparently there are two versions of the BIN file for the...

11 replies | 247 view(s)

February 25th, 2021, 01:25 PM

Hugo Holden replied to a thread Help needed with European Apple IIe in Early Apple (I, ][, ///, etc.)

Probably the bad Rifas caused a ground fault leakage condition that tripped your RCD. The fact that one electrolytic capacitor was bulging,...

3 replies | 136 view(s)

February 24th, 2021, 02:34 PM

Hugo Holden replied to a thread Commodore 1541 5.25" disk drive question. in Commodore

Thank you. It is interesting that they are out of stock of the fabric reinforced version of the belt, so they might have been a popular spare...

11 replies | 247 view(s)

February 24th, 2021, 12:42 AM

Hugo Holden started a thread Commodore 1541 5.25" disk drive question. in Commodore

I bought a 5.25" Commodore 1541 disk drive unit. I want to use it in conjunction with my AIM-65 computer. I have also bought an AH5050 board and ROM...

11 replies | 247 view(s)

February 22nd, 2021, 02:35 PM

Hugo Holden replied to a thread Need help identifying another circuit board component in Vintage Computer Hardware

I find a good supplier for these sorts of things is Digikey and only 74 cents each: ...

23 replies | 367 view(s)

February 22nd, 2021, 02:09 PM

Hugo Holden replied to a thread Need help identifying another circuit board component in Vintage Computer Hardware

It is almost certain that this capacitor is directly on a power supply line, with little else in series with it, or there would have not been enough...

23 replies | 367 view(s)

February 21st, 2021, 11:34 PM

Hugo Holden replied to a thread Need help identifying another circuit board component in Vintage Computer Hardware

Yes M is likely the tolerance.

23 replies | 367 view(s)

February 21st, 2021, 09:40 PM

Hugo Holden replied to a thread Need help identifying another circuit board component in Vintage Computer Hardware

Yes, it likely is in a supply bypass application, so you could use a 3.3uF 25V Tant or a 4.7uF if you wanted. The usual rule is don't go below the...

23 replies | 367 view(s)

February 21st, 2021, 09:31 PM

Hugo Holden replied to a thread Need help identifying another circuit board component in Vintage Computer Hardware

The black capacitor which shows a damaged casing (as Dwight predicted) is a 3.3uF 25V rated Tantalum type. The end with the taper and the + making...

23 replies | 367 view(s)

February 21st, 2021, 07:27 PM

Hugo Holden replied to a thread Need help identifying another circuit board component in Vintage Computer Hardware

I agree with Dwight. With the voltages available to the drive, it would be pretty difficult to overheat most resistor arrays of over a few hundred...

23 replies | 367 view(s)

February 21st, 2021, 01:29 PM

Hugo Holden replied to a thread 1980 Astec Power supply blues in Early Apple (I, ][, ///, etc.)

I'm a bit confused because you said it was the same under load in a previous post, but now the +5 and +12 go down under load ? Can you describe...

29 replies | 805 view(s)

February 20th, 2021, 12:55 PM

Hugo Holden replied to a thread 1980 Astec Power supply blues in Early Apple (I, ][, ///, etc.)

There could be a clue there. It suggests you are testing the supply with no load on it ? that is the only way it could take so long for the caps to...

29 replies | 805 view(s)

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