LX-626 AWR-029 wrong voltages, ATT-04-E transformer issue?

[zeferinoj]

Hello.

I'm trying to restore an LX-626 receiver. The power supply board AWR-029 had most of its components changed (actually only a few resistors are original), with parts listed here at Audiokarma.

C1 to C4 and D1 to D4 were, as far as I know, the only offended components (either shorted, corroded or in open-circuit condition), but when I tested the voltages at points 3, 5, 7 and 10, the only correct measurement was at 7 (~13.5V).



For example, Point 3 read about 38 V, when it should have read 57V.

All voltage measurements were done with these points off circuit (I'm troubleshooting one board at a time) using several ground points just to be sure.

So I'm wondering if there could be something wrong with the transformer. It's an ATT-041-E but I can't find its specs. Can someone please tell me the expected voltage between points 1 and 4, and also between 3 and 8?

Thank you very much!

All the best.
JZ

 

[larryderouin]

The SX-626 (1973 version) also uses the 141-E transformer. However that manual does not give voltages either.

The pin you are identifying as pin 3 (above pin 8) is actually pin 9. Pin 3 is the 57v output voltage to the amp section.
Pin 9 and 8 are an AC Voltage (unknown to me) as is the voltage between 4 and 1. List all voltages by pin# in a vertical format. AC VOLTAGES are to the pin pair. DC Voltage Grounded to Chassis.

Once all current Voltages are known, then the guru's can determine a course of action. Make sure you have the transistor legs in the correct holes. The new ones are most likely pinned differently from the originals. If needed get the datasheet's for the new ones from Mouser or digikey. Also Make SURE (Visually check orientation) the electrolytic caps are correctly oriented as are the diodes.

 

[zeferinoj]

Hi.

Thanks for the heads-up. Here are the readings.

PIN Expected (V DC) Read (V DC)
3 57 38,7
5 30 19,2
7 13,5 13,3
10 13 24,7

The AC voltage between points 1 and 4 and also between 8 and 9 (while not connected to the AWR-029) are 41 V AC and 36 V AC, respectively.

I've also checked the new transistors' datasheets and they match the original orientation. The caps look OK too.

Thanks.
JZ

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Just for reference, the diodes are 1N5408 and the caps are 0,01 uF, 3kV. I couldn't find any 1,4 kV

 

[zeferinoj]

Hello.

Just to wrap up this thread, everything is ok with the transformer and the recovered AWR-029 power supply board.

I was taking readings without soldering those pins to their respective loads. Once this was completed the measurements yielded the expected values.

Thanks.
Kind regards.
JZ