Pioneer Speaker Package subwoofer transformer.

[bamix]

Re: Pioneer Speaker Package subwoofer transformer.

madan1,

Please see attached pictures.

I hope they cover what you are after. There is basically one IC connected to the heat sink. I took the holding bracket off too but there was no information on that side of the IC. The board is only screen printed there as IC21.

Let me know if there is something else you would like.

[madan1]

Re: Pioneer Speaker Package subwoofer transformer.

Well, that's a surprise... I've heard about companies erasing the chip labels, but did not expect it from pioneer.
Anyway, from the pinout and the form factor, this looks like tda7294 to me and according to the documentation - everything supplying between 10 and 40 volts should do the work.
My guess is that they have been aiming at 40 volts after the rectifier bridge.


ps. just got a second look at the image and I swear I can see the ST logo and some part of the TDA label. Can you check again what's the label?

[budm]

Re: Pioneer Speaker Package subwoofer transformer.

The incandescent lamp will limit current, if the transformer has shorted winding the lamp will light up brightly. 60W incandescent lamp will be fine, it has to be incandescent lamp.
The lamp is connected in SERIES with the primary winding of the transformer.

[bamix]

Re: Pioneer Speaker Package subwoofer transformer.

You are right madan1.

I couldn't see anything with my naked (failing) eye but I looked at the original pic and can make something out. I will try and get a better image to confirm.

Give me 20 minutes

[budm]

Re: Pioneer Speaker Package subwoofer transformer.

What is the actual model number of this Pioneer sub woofer?

[bamix]

Re: Pioneer Speaker Package subwoofer transformer.

Thanks budm.

Yes, so in series as:

* Blue Wire -> Lamp -> Blue Wire -> Winding End 1
* Brown Wire -> Winding End 2

and Thermal Fuse is no longer in the circuit.

Lamp on the neutral side should be OK I think. DC is my favoured current.

[bamix]

Re: Pioneer Speaker Package subwoofer transformer.

madan1,

It is TDA7293.

Hope that helps.

[bamix]

Re: Pioneer Speaker Package subwoofer transformer.

budm,

Apologies but I missed your post regarding the sub model. I don't know that it has a model number. It was part of the Pioneer Speaker Kit boxed up as S-HS50 that was bundled with the AV Receiver I purchased, a VSX-522.

I can only find any information on line where people tried to sell them off, nothing either from Pioneer themselves or any technical data. Here's a link as an example.

I have since changed the centre speaker for a larger Klipsch unit and although it is all entry level gear it does alright for my application. Mind you, all my kids think I am going deaf .......

[bamix]

Re: Pioneer Speaker Package subwoofer transformer.

budm,

I tried the test using a 60W incandescent lamp in series. I think perhaps my connections were not solid enough but it didn't seem to work, that is the lamp did not appear to light at all.

I checked with my meter and found that I had 240v available at the Blue and Brown wires but nothing showing at the winding ends again.

I was worried that the windings had failed and was packing up the test gear when I noticed that the incandescent light globe was quite warm to the touch. So I substituted it for the lower wattage Philips LED lamp and tried again and it worked. I attached a small video as a 'rar' file for reference.

From this result can I presume that, for now, the transformer will be OK if I proceed with replacing the Thermal Fuse ?

Thanks in advance. I do realise that you must be very busy and appreciate your kind efforts.

[Agent24]

Re: Pioneer Speaker Package subwoofer transformer.

From what you have done it seems the transformer is OK.

If the transformer had shorted windings, the 60 Watt lamp you tried would have lit brightly. If the transformer was open-circuit, the LED lamp wouldn't have lit at all.

For the record though, LED lamps are unsuitable for this test as they will not limit the current in the same way an incandescent one will.

[Khron]

Re: Pioneer Speaker Package subwoofer transformer.

Good, the bulb not lighting up (maybe apart from a flash just when you turn the thing on) is what you want.

Sounds like it was just the darned thermal fuse indeed

Quite odd that the LED lamp in series(!) with the thing somehow worked, though...

[bamix]

Re: Pioneer Speaker Package subwoofer transformer.

Thank you again everybody for your valuable insights and contributions.

My Thermal Fuses are due to arrive tomorrow so I will replace the failed one and give it a shot. I will post the result. The original is soldered in, is it possible to install the replacement in the same way if I use some sort of shunt to stop the heat from getting to the fuse ? I was thinking of using a pair of Vise-Grips, a G-Clamp or similar on the leg between the fuse and the solder point. Is that the best way to approach it ?

In my trawling of the web for info on this model I found a lot of sites where people were complaining of a similar issue so I hope that the detail and structure of this thread may be helpful for someone else in the future.

Thank you so much, it is really appreciated. In fact, I found it awesome that I can reach out from right down here and have kind people from all corners of the globe lend a helping hand. If only the rest of the world worked that way....

[Khron]

Re: Pioneer Speaker Package subwoofer transformer.

Well, since the original's leads are so long and thin, i guess you could indeed get away with soldering them.

A while ago i had to replace a chunky thermal fuse (with 0.8-1mm thick legs) which the datasheet recommended crimping.

Yes, something like vise-grips should do fine - just don't totally squash the legs and risk them falling apart

[bamix]

Re: Pioneer Speaker Package subwoofer transformer.

OK, just to wrap up. The new Thermal Fuses arrived this morning.

I have carefully soldered one back in place of the original failed piece and reset the layers of insulation all the time checking that I had maintained a circuit through the windings. I reconnected the transformer to the boards and speaker and powered it up.

All good.

For the record I measured the output of the secondary winding unloaded at 60vAC between the two yellow wires. Measuring each back to the centre white wire of the connector I got 30vAC.

From that, I expect it's a 30-0-30 AC Transformer.

I expect the output is then rectified and regulated to around 24vDC to run the other components on the amplifier board.

I have had a quick look around on the Internet and it seems that this 30-0-30 type is not so common. If it fails again, might be time for the sub-woofer to go to the bin.......

Thanks again to everybody.

[Khron]

Re: Pioneer Speaker Package subwoofer transformer.

Well, the 30VAC you measured was unloaded(?), which will be higher than the "rated" voltage.

https://en.wikipedia.org/wiki/Transf...al_transformer

24-0-24VAC ones may be more common, i'd think (or whatever other values there may be, up to 30-0-30VAC).

[budm]

Re: Pioneer Speaker Package subwoofer transformer.

That means the DCV on the caps will be around 42VDC, if your line Voltage goes higher then you do not have that much head room since the filter caps are rated at 50VDC.
What is the AC feeding the unit?

[bamix]

Re: Pioneer Speaker Package subwoofer transformer.

Thanks guys.

budm, AC feeding the unit is 240v. I see your point with head room in the capacitors. Best to not to squeeze that margin at all.

Khron, understanding there are deviations from ideal, is it safe to assume then that the 'rated' voltage is always a loaded one ?

From the online content I have seen trying to find a replacement the specifications are listed differently from site to site. When I started this thread, the idea I had in mind was that given a transformer with no output and no markings, there may be a choice of 'standard' parts that would fit the bill. I can see now that the choices are quite varied and dependent solely on the properties of the components on the surrounding boards. I have learned quite a bit these past days covering this matter and for that I am very grateful.

Thanks again.

[Khron]

Re: Pioneer Speaker Package subwoofer transformer.

"Good" transformer datasheets specify a voltage regulation rating, in percent.

http://www.electrical4u.com/voltage-...f-transformer/

From my understanding, that percentage is how much higher the no-load voltage is, compared to the fully-rated-load voltage is. For example, a transformer i've selected for a project of mine has a 25% specified regulation.

https://cdn.badcaps-static.com/pdfs/...7102c93d7c.pdf

On each 6.3VAC secondary, i'd expect to see about 7.8VAC at no load.

And besides, since this transformer is from a relatively affordable(?) consumer range subwoofer, you can bet your booty it's built down to a price, same as the component parts, so the loaded voltage on your transformer WILL be considerably lower than the no-load one

Taking a pessimistic(?) 25% regulation into account, the 30-0-30VAC you measured at no load would drop to 24-0-24VAC at whatever load that transformer's rated at.

Some rule-of-thumb figures - http://www.zen22142.zen.co.uk/Design/dcpsu.htm

[bamix]

Re: Pioneer Speaker Package subwoofer transformer.

Khron,

Thanks for the additional info, you have given me some homework to do.

'To a price' are probably the keywords in this example of a cheap sub. They must have saved money by not printing any info on the transformer....

Take care.

[cubic25]

Re: Pioneer Speaker Package subwoofer transformer.

Hey all.

Sorry to revive an old thread, but I have this exact sub with a very similar issue.
I took the transformer appart, and attempted to locate the thermal fuse, only to discover that not only had the fuse disintegrated, but all the wires were burnt out too. I thought it was going to be a simple solution, such as the OP's, but it turns out that I will need a new transformer.

Can anyone suggest a transformer that will power this amp?
I can't seem to find anything on ebay. I might head into jaycar tomorrow and see what they have....
While I'm here, does anyone know if I can disconnect the standby feature on this sub? It is really annoying hearing the relay clicking every time it turns on and off.

If I can't find a new transformer, or if it is too expensive, I might just get a new active sub off ebay for the cheap.

Thanks in advance for any help.

Pic of transformer: