Power transformer for SPL Vitalizer, HAHN 305-2057

[pvision]

I have an SPL Vitalizer with a bad power transformer. The trafo is a HAHN 305-2057, made in Germany, 3 VA with a 230 primary and 12-0-12 secondary

After a bit of searching I have found a replacement but have not yet found stock in the UK. If anyone has one, or knows where to source one in the UK, I'd be please to hear. Otherwise, below are my notes which, I hope,  may help others in the future


It's a PCB-mount trafo. I have looked at data sheets and it seems as though there's a fairly standard pin configuration on a 5 mm pitch

5 - AC in    6 - 12 V out
4                    7 - see above
3                    8
2                    9  - 12 V out
1 - AC in    10- 12 V out

The pitch between pins 5 & 6 on the HAHN is 20 mm. All the replacements I can find from UK suppliers have a pitch of 25 mm. I haven't check heights yet - the HAHN trafo is only 32 mm tall

Block VB3.2/2/12 (Farnell 1131637)
Myrra 44237 (5 VA) or 44201 (3.2 VA) (Farnell 1214601 or 1214594)

I can get the Block or Myrra from Farnell. There is a UK supplier for HAHN called Ocean Grove - I have enquired about supply

The HAHN original is available from TME in Germany for £1.81 + £5.70 shipping

A close equivalent 306-3366 is available from Distrelec for €4.92



https://www.distrelec.de/en/pcb-transformer-va-12-vac-2x-hahn-ei306-3366
http://www.tme.eu/en
http://www.hahn-trafo.com/english/


Nick Froome

 

[radardoug]

The reason it failed is probably the small size. Maybe try and fit a bigger tranny? Use a wired one and just modify the unit to suit.

 

[pvision]

Replacing it with a different tranny was my first thought - much easier. I thought I'd look for a direct replacement anyway and that led into a bit of research on these PCB-mount transformers. The Germans call them printed transformers

I went on to examine the issue more closely: when I lifted the rectifier diodes the trafo output voltage went to ± 22 Volts so clearly it's OK. I then lifted the two resistors that link the PSU to the rest of the board and got + 12 Volts and -20 Volt output, so I have ordered a replacement 7912 regulator

When the rest of the board is connected the PSU outputs ± 8 Volts approx, so something is dragging the output voltage down. I suspect if I replace the 7912 and fire it up it may blow the new regulator

Nick Froome

 

[radardoug]

7912s are pretty rugged, but it sounds like the supply doesn't have to produce much with a 3VA transformer. I would replace the 7912, you know thats dead. Then fire it up quickly checking the rail volts. If they are still low you have to search for the current hog.
One way is leave it on and see what gets hot.

 

[Harpo]

...I then lifted the two resistors that link the PSU to the rest of the board and got + 12 Volts and -20 Volt output, so I have ordered a replacement 7912 regulator...

...leaving both regulators without any load connected. The negative one most often behaves unpredictable. Put a temporary 470R...1K resistor for a 12...25mA min.load across the -12V output and 0V and the negative rail might show the expected -12VDC again. Most likely the excessive load will be downstream.

 

[pvision]

I am lucky in that there are two resistors that link the PSU to the rest of the board, so have lifted those for testing. No doubt the new 7912 will put the rail voltages right

None of the chips seems fried and there are no nasty smells in the unit but, with a 3 VA transformer, nothing would get particularly hot!

All the ICs (apart from the SPL hybrids) are socketed so, when I reconnect the board, I might pull them all out for testing

Thanks for the reminder re a temporary load when testing the PSU. It's a very long time since I have fiddled with electronics and I am relearning standard procedures!

Thanks for the help

Nick Froome

 

[pvision]

To draw a line under this: I replaced the regulator, pulled out all the ICs (they are socketed) and fired it up

All OK, so I replaced half the ICs. After a couple of minutes testing I narrowed it down to the last IC (isn't it always?) that was bad. Replaced it, tested OK

Nick Froome