Dell MFP 1600n

Got this one from the owner with the hint „device is working, only toner is missing and there is no windows driver anymore“. It stood in a cellar for some years.

The 1600n is an ADF (multipage) scanner, a copier, a printer and a FAX device. It understands Postscript and PCL. It has a 100MBit/s LAN connector. Internally it has a166MHz (ARM-based) CPU and 32MB built in RAM. Firmware can be uploaded via USB and LAN. So it is an interesting device built 2005.

This printer is sold by Dell but designed and produced by Samsung. Samsung sells this printer with another name SCX-4920N.

Just from looking at it, the device looks good. So I take it with me and powered it on. No reaction.

My first idea was that this is due to a power supply fault, mostly caused by faulty power caps.  After I’ve got the service manual from Internet I was able to remove the power supply board from the bottom of the printer. The service manual says that the board must be reached from the top by removing nearly everything, but it is possible without any problem to remove the board from the bottom. Just about ten screws and some connectors.

All the device parts smelt of magic smoke.

The first problem was instantly visible. A big cap (1500uF 10V) was faulty. I replaced the cap. Examining the board shows seven 3K3 resistors in parallel which went very hot in the past, but measured ok.

One additional resistor at another place on the board (see images) also went hot but was also still ok. I supposed that this was just a follow up problem of the faulty cap and powered the device on.

The faulty cap (brown and ugly) and the resistors


R124 went also hot in the past, but looks still ok.


That was the remaining capacity from the 1500uF cap

And: tada, it booted up, made some good motor sounds and displayed that there was no toner and no paper. Good so far.

After first boot: Firmware versions

Next I hooked the device to my LAN. No connectivity. When I opened the device, I saw that the network card came out of its internal connector, maybe by brute force from the outside. I plugged it back into the connector and: LAN was working.

Checking the internal web server of the printer I saw that it had printed only ~29000 pages which is not much for a laser printer.

Controller board with network board on top (left)


So I decided to check the device further and ordered a toner cartridge. I found out that the printer part of the device is well working and fast. The scanner and copier were untested but I noticed before that the lamp never shined. Hm.

And when moving the Dell around, I heard some part tumbling inside. I found that it was a small but heavy inductance jumping around in the scanner case ;-(

So I removed the scanner part and opened it.

Cable flow for the ADF


Cable flow for display/control pad

I found that the CCFL inverter was mostly destroyed by heat coming from too much current. The PCB went very hot, the solder melt and the heavy inductivity fell out. The heat even more increased and the PCB became ash in parts.

Destroyed CCFL inverter. The transformer is still ok, but the other parts look bad. This cannot be repaired but must be replaced. It is an inverter for two lamps.



Solder side of CCFL inverter

Transistors are 2 x 2SD1857


Here the inductivity can be seen

And I found even more a problem. A small inductivity on the CCD PCB also went hot in the past. It measured ok and was not replaced.

The small inductivity with heavy signs of too much current…

The complete CCD/inverter/scanner unit. It seems to have part number 1000128-0005 and is maybe also used in Xerox C20/M20 laser MFPs and others (have not tested this)

The CCFL inverter is totally destroyed. Original is a COTEK 68200066-C000C4. Could not find that anywhere.So I decided to replace it with another CCFL inverter. I ordered several inverters (Pollin has them cheaply). Of course these replacements will not fit as they arrive in the scanner unit. But my idea was to find an inverter that works electronically well with the Dell 1600n and then etching a new PCB that fits exactly, reusing the parts from the new inverter.

Power supply to the CCFL inverter is 27.5V DC (usually inverters are made for 12V or 24V, so this is maybe wrong?). I checked the transformer which is ok and seems to work best at 114Khz.

Inverters arrived some days later. I used another COTEK inverter with 24V AC input. Reworking the PCB was not required. I had to clean all mirrors inside the CCD unit because they were blinded by the magic smoke that came from the PCB and its parts when it burned. After that I could make copies and scans. But there were new issues:

  • The burning PCB had melted the plastics of the CCD unit. During  a scan, the deformed unit collided with the cover and so the scan was not complete.
  • The copy function produced grey to black vertical lines for unknown reason. The mechanical problem that arises during scanning was not a problem here, because the CCD unit does move only a small part during copying without colliding with the cover.

Hm, the scanner/CCD unit is giving multiple problems…

This scanner/CCD part is named „ELA HOU-CCD MODULE“ numbered JC96-02759A. This unit is also used in the Samsung product SCX-4920 and other printers. So it is not hard to replace it as a complete part.

… to be continued

Innenansicht Onkyo TX-11 Receiver

Ordentliches Gerät der frühen 80er. 2×20 Watt Verstärker mit 0,08% Klirrfaktor 30-25.000Hz, UKW+MW Tuner. Siehe auch Eintrag im Radiomuseum. Japanische Produktion. Der Verstärker verwendet ein Hybrid IC der STK-Reihe (STK459).

Das Gerät erreichte mich in einem unglaublich verwahrlosten Zustand. Siehe Innenansichten weiter unten.

Das Gerät war bis auf eine defekte Skalenbeleuchtung elektrisch ok. Da die Potentiometer nicht kratzten und auch sonst mechanisch alles in Ordnung war, beschloß ich eine Komplettreinigung durchzuführen.

Die Komplettreinigung wurde als Radikalkur mit einer hart eingestellten Brause durchgeführt, mit Heißwasserstrahl. Danach war das Gerät wieder erstaunlich sauber.
Im Falle starker Verschmutzung kann man dies so probieren. Die Wahrscheinlichkeit dass das Gerät dabei kaputtgeht ist aber vorhanden. Längere Trocknung (mehrere Tage) ist auf jeden Fall erforderlich.
(Eine weitere Verschärfung ist Reinigung in der Geschirrspülmaschine, was aber für Komplettgeräte mit Plastikteilen die man sehen kann riskant ist, da sich Plastik verformen kann und aufgesprühte Farben sich lösen können. Dies war hier aber nicht nötig.)

Skalenknöpfe und Taster wurden handgereinigt.

Die defekte Skalenlampe (12V Birne) wurde durch eine rote superhelle LED ersetzt.

Servicemanual ist im Internet verfügbar.

Von außen eigentlich ganz ok…


verstaubt …



Und dann das Innere…

Schlimmer als hier im Innern geht es kaum. Ich habe noch nie ein solch verwahrlostes Gerät gesehen.


Eine dichte Staubschicht macht es fast überall unmöglich, den Leiterplattenaufdruck zu lesen. Außerdem spinnwebenähnliches Gespinst, mit Schmutz bestäubt.


Netzteil Bereich



Ohne Worte


Was muss man machen, damit ein Gerät nachher so aussieht?


Unglaublich dass der Drehkondensator noch seinen Dienst tut.




Im Bereich des Endverstärkers

Nach der Reinigung…


Nicht „wie neu“, aber doch ganz ordentlich… Tuner Bereich




Netzteil mit Trafo



Alles hat die Radikalkur überlebt. Die Frontplatte wurde  noch gesondert handgereinigt und die Taster und Knöpfe von Gilb befreit.

Nach Komplettreinigung tut das bedauernswerte Gerät bei mir im Labor seine Dienste. Hier kann man auch die neue rote LED Skalenbeleuchtung sehen.


Nach einiger Zeit zeigte sich jedoch, dass der linke Kanal Signale verzerrt wiedergab. Die Reparatur ist hier beschrieben.