Kenwood KX-W4040 cassette deck service manual or info needed - Page 1
Forum section: electronics / repair

author: Jimmy Electron
author_rank: Contributor
timestamp: September 29, 2024, 11:53:34 am
content: Hi all.Does anyone have access to either one of the Kenwood KX W4040's itself, or the service manual?I have a tape deck here which is stuck in standby and has Q78 missing. The only .pdf I can find online is $25 which is out of my price range.Any help would be greatly appreciated.

author: Jimmy Electron
author_rank: Contributor
timestamp: September 29, 2024, 05:29:18 pm
content: This thing has been sitting around for ages and one way or another it has to go.It's probably reasonable to give this thread a week and if nothing evolves then I'll scrap it for the components.If I'm honest, it doesn't seem to me that the missing transistor is the reason that the unit doesn't turn on, however without the schematic, I'm not really sure where to start looking. The power supply section has one +12v and one +15v 78xx series regulators which are both fine. I haven't really tested the multitude of electrolytics nor semiconductors. There is one relay which appears to be activated from tape deck A and not likely to turn on the whole unit.Working back from the power button, one side leads to I/O Port, pin 14 on the 64 pin main microprocessor IC, a Kenwood branded M50946-109SP, although which pin it passes through after that is another question? The other side of the power button goes back to pin 56 which is a high-voltage I/O Port.As it's Sunday, I'll have another look and follow up here if anything else comes to light.

author: elantric
author_rank: Contributor
timestamp: September 29, 2024, 06:26:03 pm
content: https://www.ebay.com/itm/203917543329

author: Jimmy Electron
author_rank: Contributor
timestamp: September 29, 2024, 06:33:48 pm
content: Thanks for that, only I am currently in Brazil and with the communist government there is 100% import tax not only on the item but then also the postage, hence the need for a .pdf

author: David_AVD
author_rank: Super Contributor
timestamp: September 29, 2024, 08:43:46 pm
content: Is the Kenwood KX-W4050 model similar enough?

author: Jimmy Electron
author_rank: Contributor
timestamp: September 29, 2024, 10:50:46 pm
content: Quote from: David_AVD on September 29, 2024, 08:43:46 pmHi David,unfortunately not, but many thanks for the suggestion.I had been looking through the 4050 and 4060 manuals in that hope, but there are many differences, not least that the main processor chip is of a completely different type, being 64 pin as opposed to the 80 pin in 5060 and 6060..

author: Jimmy Electron
author_rank: Contributor
timestamp: September 30, 2024, 01:25:20 am
content: Last post for today.Probing deeper into the circuitry, one side of the relay coil in fact goes direct to the centre pin of Q78, the missing transistor, so 100% this transistor needs to be identified in order to be replaced.The other side of the coil is the VCC supply rail running at just under 15v and connects to other components such as an LA3246 stereo preamplifier for double cassette players.

author: coromonadalix
author_rank: Super Contributor
timestamp: September 30, 2024, 02:25:52 am
content: check this one for similarities ?https://elektrotanya.com/kenwood_kx-w4080_kx-w6080.pdf/download.htmlthey loved to use the same decks upon many models

author: David_AVD
author_rank: Super Contributor
timestamp: September 30, 2024, 05:05:14 am
content: 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?

author: jonovid
author_rank: Super Contributor
timestamp: September 30, 2024, 05:19:41 am
content: on us.archive.org is this pdf linkhttps://ia802309.us.archive.org/16/items/manual_KXW4050_SM_KENWOOD/KXW4050_SM_KENWOOD.pdf

author: Jimmy Electron
author_rank: Contributor
timestamp: October 01, 2024, 01:17:28 pm
content: Quote from: David_AVD on September 30, 2024, 05:05:14 amActually, 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 microcomputerThe Collector connects to the opposite side of the relay coil to the 15v supply railThe Emitter connects to VSS (0v) at pin 32 of the microcomputerThere 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.

author: Jimmy Electron
author_rank: Contributor
timestamp: October 04, 2024, 01:22:10 am
content: Quote from: jonovid on September 30, 2024, 05:19:41 amUnfortunately 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.

author: wasedadoc
author_rank: Super Contributor
timestamp: October 04, 2024, 10:59:29 am
content: 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.

author: Jimmy Electron
author_rank: Contributor
timestamp: October 04, 2024, 02:19:42 pm
content: Quote from: wasedadoc on October 04, 2024, 10:59:29 amHi .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

author: Jimmy Electron
author_rank: Contributor
timestamp: October 06, 2024, 12:27:23 am
content: Just a final update.Am giving up on this and gonna strip it for components and parts.Thanks for all the suggestions.