Pioneer DC-Z92 Stereo Double Cassette Tape Deck Amplifier - Transformer problem

[JohnMcC]

Hi,

My beloved Pioneer DC-Z92 Stereo Double Cassette Tape Deck Amplifier has blown due to a voltage supply surge of 380 volts AC instead of the usual 240 volts AC !!!


The transformer "Pioneer ATT1092 A JA 30A SMD" has blown on the primary coil side, and Pioneer no longer sell these transformers !!!
There is absolutely no reading on 10K ohms across the primary coil.
I cannot find any details (on the internet) about the transformer either.

I am trying to establish what the voltages are on the secondary side of the transformer.
I believe there is +5v and -24volts on the downstream circuit board (by looking at components).............but I have no idea what the transformer used to produce on the secondary side. (I believe the primary side catered for 110v AC as well as 240v AC, but I am not sure)


I have the service manual which is in the link, but this circuitry is far beyond my capabilities to decipher. Photos are in the link as well.

https://1drv.ms/f/s!ArIK6n3A4oCfgaAPUkNjPiPjRObhrw

As the transformer is no longer available from Pioneer, if I could establish the voltages and wattage of each secondary winding, and which pin it went on....................my intention would be to replace the transformer with multiple transformers and connect them with wires (so the transformers would no longer be surface mounted on the circuit board. This is of course if nobody has a better idea. All I wish if for this deck to work again !


Any help would be most appreciated.

Thank you

John

 

[spec]

Hello again John- another interesting thread.

spec

 

[Les Jones]

Hi John,
I have copied the schematic of the power board from your manual.

This is the part that shoul;d be most help. The top secondary winding is marked as 4.4 volts. The middle one will be about 24 to 27 volts and the bottom one will be about 6 volts.
Top marks John for providing excellent information.

Les.

 

[JohnMcC]

Great Les.
I saw the 4.4v for myself, but I do not know how you have established the other 2 windings.
Also I don't know what VA I will need for replacement transformer or transformers ?

As this drawing above is only schematic............how do I establish which terminal on the board corresponds to which voltage ?
On the primary side of the transformer there are 5 pins and they are all connected to the board..............why would that be ?


Thanks
John

 

[Les Jones]

Hi John,
The 6 volt winding is regulated down to 5.5 volts by a regulator with a number something like ???78M056 so I think this will be a 1 to 1.5 amp regulator to 5.6 volts output. It would require about 8 volts DC input so 6 volts ac when rectified and smoothed would provide this. The winding providing the 27 volts DC is estimated by the same method. I suspect this will be at a fairly small current as the first smoothing capacitor is only 220 uF (I would guess 200 mA max.) The thing that concerns me is that I think the 4.4 volts AC will be feeding the filaments of the fluorescent display and this voltage would have been higher that this while the mains was high so it is posible the display could have been destroyed. I have just had a thought about the transformer. Some transformers are protected by a thermal fuse whick may be under the insulation tape on the windings. I will have a closer look at the pictures. Identifying the pins on the transformer should be easy by looking at the etch side of the board and seening which components they connect to.

Les.

 

[spec]

Looks like there are two mains transformers, presumably one transformer for the cassette electronics and another transformer for the audio amplifier. Each transformer has its own mains fuse:

 

[spec]

Just one point about transformers John- you can invariably fit a larger VA transformer. Any replacement transformer needs to be at least the VA of the original though.

spec

 

[spec]

Look like the top transformer is:
(1) Primary: 240V RMS
(2) Secondary #1: 4V RMS
(3) Secondary #2: 32V RMS
(4) Secondary #3: 12V RMS

spec

 

[alec_t]

the bottom one will be about 6 volts.

It may be higher: the voltage on the input of regulator IC:002 is shown as 14V.

 

[spec]

If the primary of the top transformer has gone open circuit, you could put 4V RMS from another source (transformer), across the 4V terminals and measure the other seondary voltages.

spec

 

[Les Jones]

Hi Alec,
I think you are right. I was reading those numbers as test point numbers rather than voltages. I was planning to read through the text to find what voltages were on them. I was just about to suggest what spec had suggested in post #10 but then noticed his post.
John, if you remove the transformer from the board it may be worth looking closely at the transformer to see if there is any lump in the insulation tape round the winding that could be a thermal fuse.

Les.

 

[JohnMcC]

Thank you Les and Spec,

Looks like there are two mains transformers, presumably one transformer for the cassette electronics and another transformer for the audio amplifier. Each transformer has its own mains fuse

I have been and had a look.............and yes there is another transformer..............looks like that is blown as well.
Please refer to attached photos.
Terminals B is power in side (fuse-side) and there is no continuity on x10K ohms
Terminals A looks like the 12v output side..........and there is continuity

So probably this transformer is burnt out as well ??

Just one point about transformers John- you can invariably fit a larger VA transformer. Any replacement transformer needs to be at least the VA of the original though

Yes, that I know thank you.

Kind Regards,
John

 

[JohnMcC]

If the primary of the top transformer has gone open circuit, you could put 4V RMS from another source (transformer), across the 4V terminals and measure the other seondary voltages

I do not have another source with 4v RMS

John, if you remove the transformer from the board it may be worth looking closely at the transformer to see if there is any lump in the insulation tape round the winding that could be a thermal fuse.

I was recommended to do this on the microwave transformer by a friend .............and it was explained I should remove the insulating tape..........I totally mucked up the transformer ! The wires were so fine that just pulled out, and I was trying to be extremely careful. By the time I had finished...........I found no thermal fuse.

 

[Les Jones]

If there is room in the Hi Fi for an extra transformer then you could feed 12 volts AC into bottom winding (That supplies the 12 volts for the relay and 5 volts for the electronics.) If you try this disconnect the 4.4 volts output (For the display filaments) in case the voltages from the original transformer are different to the assumed values.

Les.

 

[JohnMcC]

Hi Les,

If there is room in the Hi Fi for an extra transformer then you could feed 12 volts AC into bottom winding (That supplies the 12 volts for the relay and 5 volts for the electronics.) If you try this disconnect the 4.4 volts output (For the display filaments) in case the voltages from the original transformer are different to the assumed values.

Les.

I am sure I could make room somewhere in the box for additional transformers.
I would have to buy a 12 volts AC supply.
Presumably you are talking about connecting a new 12vAC transformer to the output (secondary coils) of the large transformer "Pioneer ATT1092 A JA 30A SMD" (and not the little black transformer).

Thanks,
John

 

[JohnMcC]

Presumably you are talking about connecting a new 12vAC transformer to the output (secondary coils) of the large transformer "Pioneer ATT1092 A JA 30A SMD"

To be clearer.............Presumably you are talking about connecting a new 12vAC transformer to the output terminals from the secondary coil of the large transformer "Pioneer ATT1092 A JA 30A SMD"

 

[Les Jones]

Hi John,
When you said that there was another transformer (In post #12) I thought that you were talking about a larger transformer than the ATT1092. (When I first read post #12 I thought you had inserted the wrong pictures by mistake as they show the ATT1092 tranformer.) Looking through the service manual I thought you were referring to item 2 on the exploded view on page 6 (As shown as 6 of 73 at the top of acrobat reader.)
What is the little black trnsformer you are talking about ?

Les.

 

[JohnMcC]

Hello Les,
No, sorry................I was talking about the little voltage convertor........I have put terminals A and Terminals B in red on the photo.........it is that little black voltage convertor that I was talking about
The other larger transformer ATT1092 is also faulty on the primary.

If this is not clear, please just tell me, and I will try again.

It was Spec who said "Looks like there are two mains transformers"...........so I went looking for another one inline with the fuse...........and found the little black voltage convertor !

Many thanks
John

 

[Les Jones]

Hi John,
The black thing with A & B pointing to it is a relay. (I am assuming this controls the power to the main transformer.)

Les.

 

[spec]

Here is a 4.5-0-4.5 transformer: https://www.ebay.co.uk/itm/CTFC6-4-...a8e9cc8&pid=100005&rk=3&rkt=6&sd=142129561727

There are other transormers on the net for the other voltages.

But this would mean a total of 3 transformers for all the voltages.

Would this be acceptable?

spec