Help with Symetrix 544 power transformer

[Davebassman]

HI,

I friend have an old Symetrix 544 comp. But the power transformer is burned. So, I need a replacement, the problem is that I have no idea what type of transformer is. The manual have some schematics, but is unreadable. The only that can help, maybe are the voltage regulators.

78M12
79M12

78M15
79M15

Anybody can help?

Thanks.

[nevetslab]

I have some Symetrix Compressor/Limiters of my own here...501's, and an earlier CL100, amongst many other Symetrix gear. Looking at the PCB layout, I'm guessing your DC current load for the IC regulators is around 350mA. As two of the IC regulator IC's are free-standing, and not mounting to any heat sinks (probably the LM7812M/LM7912M's, the replacement transformer you'll need will need to be on the lower side of unregulated DCV, or you'd need larger heat sinks for the LM7815/LM7915 regulators. 30VAC CT (120VAC Primary), around 12VA would probably suffice. Unless Symetrix happened to still have one of the 120018 power xfmrs, you'll have to find one that can mount to the side wall of the chassis, and fit into that cavity occupied by your failed power xfmr. I don't see enough space in there for a small Toroid. I haven't looked at available sources to see what's available. You'll have to get mechanical measurements on the thickness of your xfmr, as that dimension will be critical for it to retrofit into the chassis.

[Davebassman]

I have some Symetrix Compressor/Limiters of my own here...501's, and an earlier CL100, amongst many other Symetrix gear. Looking at the PCB layout, I'm guessing your DC current load for the IC regulators is around 350mA. As two of the IC regulator IC's are free-standing, and not mounting to any heat sinks (probably the LM7812M/LM7912M's, the replacement transformer you'll need will need to be on the lower side of unregulated DCV, or you'd need larger heat sinks for the LM7815/LM7915 regulators. 30VAC CT (120VAC Primary), around 12VA would probably suffice. Unless Symetrix happened to still have one of the 120018 power xfmrs, you'll have to find one that can mount to the side wall of the chassis, and fit into that cavity occupied by your failed power xfmr. I don't see enough space in there for a small Toroid. I haven't looked at available sources to see what's available. You'll have to get mechanical measurements on the thickness of your xfmr, as that dimension will be critical for it to retrofit into the chassis.

I complete agree with you. I mounted two transformers in series, only for checking voltages and power consumption. And on each secondary winding have 180mA, so the total mA will be 360mA more or less. So, yes a 15-0-15V 12-15VA will do the job. The problem is to find some transformer that can fit into the enclosure. The toroidal that I found can't fit.

The other think that I can do, is to use some external transformer like the ones used with mixer consoles:

https://www.thomann.de/es/behringer_psu5_eu.htm

But I don't like so much...

Thanks.

[Davebassman]

I think this can fit:

https://www.hammfg.com/files/parts/pdf/229B30.pdf

[nevetslab]

I think this can fit:

https://www.hammfg.com/files/parts/pdf/229B30.pdf

The only problem I see with this is the both the lead spacing AND the pinout at both primary and Secondary. I'd bet both are NOT the same as the original xfmr. One other attribute of this style xfmr. Higher radiated stray fields than the EI core xfmr you had. So, take a close look at the pinout of the xfmr. I'm assuming the 12V regulators are using the same Secondary windings as the 15V regulators. I looked at the schematics I have on my 501 Compressor as well as my 528 Compressor/Gate/Expander, and the pinouts are different. As you noted, you can't read the pinout on the schematic. So, you'll have to trace the PCB layout to identify all four connections on the split primary, as well as the split secondary.

I've attached these two schematics for reference;

501 Compressor Sch.pdf
Symetrix 525_sch.pdf

[Helmholtz]

In principle the frame core of the Hammond PT should allow for low stray flux. Also depends on how they arranged primary and secondary. When they say "low coupling" they probably mean low primary to secondary capacitance, which is good redarding EMI.

[Davebassman]

I know that the pinouts are different! I think it's impossible to find a transformer with the same pin spacing and pin arrangement that the old one has. I need to do some modifications. However this hammond low profile transformer, allow me to design some kind of pcb to mount over the original pcb. Yes, the 12V and 15V regulators uses the same secondary windings.

https://ibb.co/wpn8rjF

It's a a simple symmetric power supply. Or I'm missing something? So, I use the secondary windings in series to create a CT that goes to ground. Like the schematic shows.

[Davebassman]

This is the idea that I have:


Make a PCB and manually wiring each winding to corresponding motherboard pads.


And glue the new pcb over the motherboard. Is the only idea that I have.

[nevetslab]

Have you already purchased this transformer for the project? As the physical shape of it is vastly different, and you need to run wires from it's PCB terminals, whether directly or from a mating circuit board yet to be fabricated, getting it all to fit looks more challenging than doing a bit more searching for an EI core xfmr that could be mounted to the chassis side wall, occupying the same relative space as the original xfmr that failed.

I looked thru Hammond's alternative core xfmr's, and didn't see anything that would fit into a 1U chassis. If this Symetrix 544 is a 2U chassis, then I'd suggest the Hammond 166G30 30VCT-15VA

Hammond 166G30_30VCT_15VA.pdf

The thickness of this xfmr is 1.63", which if the chassis is 1U, it woudn't even fit between the top of the PCB and the top cover. I just looked up the Symetrix 544, and see it IS indeed 1U chassis. So, disregard THIS xfmr.

In looking at your Hammond 229B30 xfmr's drawing, dimension C LOOKS like it's the space between the plastic bobbin, discounting the added height of the PCB pins. I can't imagine you have more than an 1.25" above the PCB in the chassis, I'm guessing the PCB terminals would be hitting the inside of the top cover, if this were sitting face up on the PCB. Arrggghhh!

I did build a small xfmr package to power a Symetrix SX304 Headphone amp, which ended up having an IEC AC Mains panel connector and an XLR to DIN connector to route the power into it, not having the original wall wart to power it. Nice diecast zinc box, solid, allowed use of a simple EI core xfmr to be fitted into it. Not a perfect solution here, but, getting an off-the-shelf power xfmr into this unit is a challenge.

What's the dimension between PCB surface and the inside of the top cover? Some parts on the top side of the PCB COULD be moved to the bottom side of the board. For that matter, getting an appropriate-sized toroidal xfmr that could fit into that space, with insulation between PCB top surface and the xfmr, the leads COULD be soldered in on the bottom side of the PCB. I'll have a look at a few vendors's products. Hammond isn't the only one out there.

[nevetslab]

I found a Telama 30VCT 15VA Toroidal Xfmr that might fit the space. Digi-Key P/N 1295-1065-ND, Telema P/N 62053. I've attached the data sheet for it, though on that sheet, it's called out as 60053. Size is 58mm OD x 24mm H. Cost via Digi-Key is $24.07 + shpg/tax.,

Talema Minature Toroidal -0015VA.pdf

[The Dude]

Have you tried contacting Symetrix to see if they have the part available?

[Davebassman]

Have you already purchased this transformer for the project? As the physical shape of it is vastly different, and you need to run wires from it's PCB terminals, whether directly or from a mating circuit board yet to be fabricated, getting it all to fit looks more challenging than doing a bit more searching for an EI core xfmr that could be mounted to the chassis side wall, occupying the same relative space as the original xfmr that failed.

I looked thru Hammond's alternative core xfmr's, and didn't see anything that would fit into a 1U chassis. If this Symetrix 544 is a 2U chassis, then I'd suggest the Hammond 166G30 30VCT-15VA

[ATTACH]n912173[/ATTACH]

The thickness of this xfmr is 1.63", which if the chassis is 1U, it woudn't even fit between the top of the PCB and the top cover. I just looked up the Symetrix 544, and see it IS indeed 1U chassis. So, disregard THIS xfmr.

In looking at your Hammond 229B30 xfmr's drawing, dimension C LOOKS like it's the space between the plastic bobbin, discounting the added height of the PCB pins. I can't imagine you have more than an 1.25" above the PCB in the chassis, I'm guessing the PCB terminals would be hitting the inside of the top cover, if this were sitting face up on the PCB. Arrggghhh!

I did build a small xfmr package to power a Symetrix SX304 Headphone amp, which ended up having an IEC AC Mains panel connector and an XLR to DIN connector to route the power into it, not having the original wall wart to power it. Nice diecast zinc box, solid, allowed use of a simple EI core xfmr to be fitted into it. Not a perfect solution here, but, getting an off-the-shelf power xfmr into this unit is a challenge.

What's the dimension between PCB surface and the inside of the top cover? Some parts on the top side of the PCB COULD be moved to the bottom side of the board. For that matter, getting an appropriate-sized toroidal xfmr that could fit into that space, with insulation between PCB top surface and the xfmr, the leads COULD be soldered in on the bottom side of the PCB. I'll have a look at a few vendors's products. Hammond isn't the only one out there.

That's how I feel... Arrrggghhh!!

Yes, my last chance is to use an external transfomrer.

I found a Telama 30VCT 15VA Toroidal Xfmr that might fit the space. Digi-Key P/N 1295-1065-ND, Telema P/N 62053. I've attached the data sheet for it, though on that sheet, it's called out as 60053. Size is 58mm OD x 24mm H. Cost via Digi-Key is $24.07 + shpg/tax.,

[ATTACH]n912187[/ATTACH]

no... max diameter that the board allow is 5 cm.... I search a lot of toroidals, Telema inclusive.

Have you tried contacting Symetrix to see if they have the part available?

Yes, out of stock...

I hope that I have some space out of the board. So a 6.5 x 5 x 3.2 cm can fit. The hammond has 6.4 x 5.1 x 2.7 cm

[nosaj]

Ok I'm going to say it.. Have you sussed out the idea of rewinding the transformer. I will also say I have missed what the voltages were on the transformer unloaded. Are we sure the PT is toast.

nosaj

[Davebassman]

Ok I'm going to say it.. Have you sussed out the idea of rewinding the transformer. I will also say I have missed what the voltages were on the transformer unloaded. Are we sure the PT is toast.

nosaj

Yes! It's totally burned, and the former core from secondary winding are broken. So, with the old one there are nothing to do.

[nosaj]

Yes! It's totally burned, and the former core from secondary winding are broken. So, with the old one there are nothing to do.

I would talk to a transformer shop I mean like actually talk to one on the phone. Have your dimensions I'm sure you can get closure a lot faster that way.
nosaj