Sony WM-D6C dc converter

[saxmaniac]

Yes it's connected to the 6v supply, base should be approx 5.4v and emitter drives the motor with approx 2.3v

[saxmaniac]

Sorry ignore above post I was answering an earlier question
In the absence of any other info you should be able to work out the pin layout of q601
Collector is 6v directly from the supply
Base is connected to pin 15 on ic 601
Base connected to the motor
So multimeter checks will sort that out
The thing to do is replace it and see what happens

[Mooly]

Originally Posted by saxmaniac

Sorry ignore above post I was answering an earlier question
In the absence of any other info you should be able to work out the pin layout of q601
Collector is 6v directly from the supply
Base is connected to pin 15 on ic 601
Base connected to the motor
So multimeter checks will sort that out
The thing to do is replace it and see what happens

The Emitter connects to the supply, the Collector is the 'output' and goes to the motor

[saxmaniac]

Sorry again I don't know how I managed to write that, good job someone's checking!!

[Walkmann]

OK,

going to have a go at replacing Q601, have ordered a replacement 2SB798 off of ebay and one each of the suggestions BC640 and ZTX753 so let's see what happens

[Goldieoldie]

Be careful to check the lead outs on the transistors as the substitutions could well be different
Ie,check by looking at the data sheets which lead is emiter,base,collector
Rs have the data sheet for the ztx On their website

[Walkmann]

no have already clocked that so which ever transistor I try will certainly check the lead outs - thanks

[Walkmann]

having difficulty finding the exact SMD now -2SB798 - so have had a 2SA1797Q suggested as an alternative. Specs look relatively similar am I missing something other than the lead config? Will order one each of the suggestions BC640 and ZTX753 in any event.

[Mooly]

I wasn't aware it was an SMD device tbh. The manual I looked at said a 2SB1063 for Q601 which didn't sound right as that is quite a large package.

In the first instance I would just have tagged 'anything' remotely suitable in it's place as an initial test rather than trying to locate the original device type.

[Goldieoldie]

Must be a later model to the one I repaired as it was not a smd
From memory the ztx I used was a 100v 2a device ,nothing special

[Walkmann]

OK, so an update and it is good news.

Thanks to all here and the help, it was indeed Q601, had to install an alternative but the motor now turns and am just taking a deep breath before checking everything out, speed, flutter etc.

[Mooly]

Well that is good news, well done.

[saxmaniac]

Thanks for reporting the outcome nice to know how the story ends!

[Walkmann]

Hi all,

Unfortunately all is not so well as first thought.

I have the motor running, I have ungunged the tyre mechanism that drives the Rew/FFd function and miracle of miracles there is now output through the headphone socket etc. This D6C must have been in storage for a very long period judging by how stiff the mechanism and various electromechanical parts were!

Almost there;however, the motor is running fast approximately 2.5 times faster than it should. By all accounts and the various posts around it has to be IC601; however, is there any other thing it could be, I should check before I swap out the IC bearing in mind the DC-DC converter is fine?

And again all encouragement and assistance is greatly appreciated.

[Goldieoldie]

I’d be surprised if it were not the ic !
This is caused by applying neg earth power supply’s (should be pos earth)
Instant death to this motor control ic
Could be something else ,check the connections of the coil by capstan which supply’s pulses to the chip
The ic is easily available on eBay and not expensive
Use quick chip to remove the chip ,makes the job very easy

[Mooly]

Well it could be the chip but I wouldn't automatically jump for that.

If you isolate pin 15 (just unsolder that one pin) that feeds the base of your Q601 then the motor should not run at all. Or unsolder the base but be sure to unsolder the correct pin.

I'm just trying to cover the possibility of something being amiss with the newly replaced transistor in some way.

[Walkmann]

OK thanks for replies will check the transistor and the coil first before fiddling with the IC but what am I checking with the coil and how?

[Goldieoldie]

With the coil check for continuity and the wires are attached to the circuit board
They are thin and can come off on their own !

[Mooly]

Ideally you would use an oscilloscope to look at the 'tacho' signal entering the chip on pin 1 although the manual doesn't seem to show a value. I would expect a clean looking sine wave of perhaps a volt or so peak to peak amplitude.

You should check that the speed adjusting presets are OK and have not been twiddled. Try putting it on manual adjust and seeing if the user speed control knob has any effect... after checking the transistor.

[saxmaniac]

I think the coil should measure 600 to 800 ohms if I remember right. There's a couple of black wires from under the flywheel so follow them to find the ends. I don't know if an open circuit coil shuts down the motor or runs it flat out. See if the speed tune setting works, this would indicate that the ic works. As previously said, check there's nothing wrong with the transistor you fitted, I presume you fitted a pnp type?