Electronics > Repair
Kenwood KX-W4040 cassette deck service manual or info needed
Jimmy Electron:
--- Quote from: David_AVD on September 30, 2024, 05:05:14 am ---Well, you can work out if Q78 is NPN or PNP and the pinout. The footprint will give you an idea of the original package type and probable current rating. Pick something with a 50V rating and go from there?
--- End quote ---
Actually, I'm not sure about Q78. Looking through the other manuals, Kenwood used a lot of the 'S type' package, with the built -in resistors.
It seems they were particularly keen on the UN4212 and UN4112 22kΩ ones for NPN and PNP respectively.
Anyway, I believe that the pinout from left to right is Base, Collector, Emitter.
Assuming that;
The Base goes to I/O Port P4, pin 14 on the M50940-109SP CMOS microcomputer
The Collector connects to the opposite side of the relay coil to the 15v supply rail
The Emitter connects to VSS (0v) at pin 32 of the microcomputer
There is no signal at all coming from pin 14, and if I jump the relay coil, then nothing new happens on the W4040. All there ever is is a single LED showing.
Granted, the unit is currently disassembled, with just the main board and transformer, so I suppose it is 'possible' that the cassette players and relative pcb's need to be connected in order for it to turn on, however I'm not convinced.
This is where a manual would help.
Jimmy Electron:
--- Quote from: jonovid on September 30, 2024, 05:19:41 am ---on us.archive.org is this pdf link
https://ia802309.us.archive.org/16/items/manual_KXW4050_SM_KENWOOD/KXW4050_SM_KENWOOD.pdf
--- End quote ---
Unfortunately the 4050 is only similar from the outside. Completely different circuitry and boards on the inside.
It's looking like this 4040 is gonna be scrapped, which is a shame as it is in spotless condition, although the parts which it will 'donate' shall help other devices come back to life in the future.
I must say, I'm surprised that the .pdf manual is so hard to source at a fair price considering how many 4040 service manuals are for sale in the paper format.
wasedadoc:
I would reassemble and short the collector and emitter pads for the missing transistor. If that brings it to life, test if the voltage fom the micro to base pad changes with operating buttons. If yes what max voltage does it reach? Think about trying an NPN transistor and series base resistor.
Jimmy Electron:
--- Quote from: wasedadoc on October 04, 2024, 10:59:29 am ---I would reassemble and short the collector and emitter pads for the missing transistor. If that brings it to life, test if the voltage fom the micro to base pad changes with operating buttons. If yes what max voltage does it reach? Think about trying an NPN transistor and series base resistor.
--- End quote ---
Hi .
Thanks for the suggestions.
I had already shorted the transisitor and whilst yes, it activates the relay, the cassette deck remains the same, as in lifeless.
Probing deeper in fact, the other side of the relay coil is connected to tape deck B which makes me think that the relay is perhaps only operational when 'record' is selected, and not activated when turning on the unit. Apart from the coil terminals the relay has six other pins, making it DTDP (double track double pole) and both the input pins also connect back to tape deck B via a ribbon. At a quick glance, at least two of the output pins connect to an LA3246 which is a stereo preamplifier for double cassette decks.
I think it is now reasonable to assume that the relay has bugger-all to do with switching the unit on.
So, thinking elsewhere... something I should have done before, however I'm gonna thoroughly check ALL the power supply section before calling it a day.
Wish me luck
Jimmy Electron:
Just a final update.
Am giving up on this and gonna strip it for components and parts.
Thanks for all the suggestions.
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