I'm having a little hard time trying to map some electronic components in a C128D power supply unit. The PSU is the Schaffer BV 223-5-04008 (schematic) provided with the German version of Commodore 128D. The board has no annotation and there are some mixed components from two different manufacturers that I cannot recognize or found for reference. In particular I am not able to found information about the one in this image:

Component from 223-5-04008

Does anybody have information about this maker?

The complete board is here below:

front of board

Components I can't identify are made by Schaffer (the blue box up in the picture) and the green ones (except for the obvious ones like the resistors near the IC).

This is the back of the board (image not mirrored):

back of board

Schematic Source: Bo Zimmerman

Additional pictures that could help:

Semi-transparent "back" view

Semi-transparent "front" view

  • 1
    Zoom out a little bit to see what part on the schematic you mean or at least mark which component it is in the schematic if you know which component it is.
    – Justme
    Commented Apr 21, 2022 at 11:24
  • 3
    You might try asking over on electronics.se; use the identification tag. Commented Apr 21, 2022 at 11:36
  • @AlexHjnal thank you, I will probably ask there if I cannot find answer here. Since is a PSU for a retrocomputer it could be a useful reference for other people. Commented Apr 21, 2022 at 12:51
  • FWIW they look like class X or Y safety capacitors to me. Commented Apr 21, 2022 at 12:57
  • Could you include a photo of the back side of the board as well? Commented Apr 21, 2022 at 12:58

2 Answers 2


The green caps marked F1772-410 are Class X1 type safety mains filter caps, rated 100nF and 440VAC, C1 and C4 in the schematic.

The green caps marked F1710-222 are Class Y2 type safety mains filter caps, rated 2.2nF and 300VAC, C2 and C3 in the schematic.

Based on these ROE and ERO logos, these capacitors are made by Roederstein, now part of Vishay.

The blue box that reads Schaffer 282/131 must be the pulse transformer TR2 in the schematic.

  • Wow, I'm really impressed. Thank you. Do you know who is the manufacturer? I can read EAO, but I'm not sure. Commented Apr 21, 2022 at 13:33
  • 2
    Nearly all caps have visible ROE or ERO logos, so they were manufactured by Roederstein, now part of Vishay. But the manufacturer is not important, the important part is that some of the capacitors need to have special safety class rating of the correct type. Which is why mains voltage equipment should be serviced only by people who know what they are doing, as those that don't know what they are doing can make devices hazardous to people and other equipment just by swapping in an incorrect type of capacitor.
    – Justme
    Commented Apr 21, 2022 at 14:17
  • @AyeieBrazo The first google result for "F1772-410" is to a parametric search at Mouser (a major US parts distributor). You'll compatible parts there. Commented Apr 21, 2022 at 14:18
  • Hi Alex, thanks for pointing me, I guess the components itself are not failed, I have no voltage on output pins, but I think the problem is elsewhere. As you can see I have already changed a couple of capacitors (the originals had bumps) and I also changed the fast switching diodes. I just needed to better understand other components to start investigating the failing one (or ones). Commented Apr 21, 2022 at 14:55
  • Check all the resistors. Esp R15. C8 is also a suspect. If you have no means to measure its ESR, just replace it.
    – Kartman
    Commented Apr 25, 2022 at 11:42

Components I can't identify are ... the green ones (except for the obvious ones like the resistors near the IC).

All of the boxy green components are capacitors. The ones at the left (mains voltage) side are class X and Y safety caps as detailed in @Justme's answer. The (visible) ones near the IC are marked .22K which is 0.22µF ±10% (K = 10%) and .47K63 which is 0.47µF ±10% 63V. The small green component below and to the left of the latter is a ceramic cap (C101? It's between R101 and the blue wire marked frei on the schematic).

Other things of note:

  • The loop of wire at the bottom-right (next to the red wires) is R124 and is a low-value resistor. The white ceramic block above it is R129, another low-value resistor. Both should be able to pass a significant amount of current.

  • The grey orbs each with one black end are diodes as are the three-pin (TO-220?) parts screwed to the large heatsink (D102 and D103) amongst other places.

  • The blue cylindrical axial components with a black band at the end (two to the right of the IC and one to the left of it by the variable resistor) are Zener diodes1. The one with visible printing (4•7) is probably 4.7V (it's DZ101 on the schematic). As with all diodes, the black band marks the cathode. Zeners, however, are designed to have precise2 reverse breakdown voltages and so are almost always used in a reverse-biased configuration with the cathode on positive side and anode on the negative (the opposite from how diodes are usually used)3.

  • The wire colors at the right of the board/schematic are:

    • ge = gelb = yellow
    • rt = rot = red
    • sw = schwarz = black
    • or = orange = orange
  • The DIP-14 IC appears to be an LM2901 quad comparitor (or a similar chip).

Board with components labeled Traces and symbolic components (top view)
Board with components labeled Traces and symbolic components (top view)

1 Thanks to @Justme for correcting me on that.

2 Well, fairly precise. The breakdown voltage is current-dependent (the knee current) and lower-voltage ones tend to have a less pronounced knee than higher-voltage ones. This becomes most apparent with Zeners rated less than around 5V or so. See here for a more detailed discussion.

3 In a pinch, Zener diodes can be used as normal diodes (with about 0.7V forward voltages) provided one takes the reverse-biased characteristics into account.

  • Seriously, the blue axial components are not electrolytic capacitors. They are clearly diodes. Most likely Zener diodes to be exact. The black band is the cathode end.
    – Justme
    Commented Apr 22, 2022 at 9:30
  • Alex: axial electrolytic caps could be C111, C112 and C115 in scheme (cells C3 and C4)? The gray orbs could be DZ101, DZ102 and DZ103 (cells C3 and E3)? There's another Zener in scheme at E6. Switching diodes are all 1N4148 there are total of five on board. Commented Apr 22, 2022 at 9:35
  • Oh and there is one green high power resistor, so not all green components are capacitors. It is just in the shadow of the transformer. @AyeieBrazo There are no axial caps anywhere. Gray orbs are on mains side and there is only one Zener on mains side and it is likely the component that is not visible from behind the heat sink.
    – Justme
    Commented Apr 22, 2022 at 9:50
  • @AlexHajnal It can't be, as the only PTC is the blue disc right next to mains input connector.
    – Justme
    Commented Apr 22, 2022 at 11:33
  • @AlexHajnal There are no copper traces or room to allow VDR1 to be under TR3. The only place for VDR1 is right next to the fuse, and it seems to be removed or not present to begin with.
    – Justme
    Commented Apr 22, 2022 at 20:14

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