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EAR 834 zener's temperature hot?

Just finished the build on my ear clone. Powered up normally on 60 watt dim bulb, and voltages low as expected.

Full power, I measured 292 at the power supply, and 5.9 on the heaters. Let it warm up for an hour and played a few records.

Probe around with temp IR temp gun, everything seems normal except for the zener ladder, they are 180F ! I used 1n5373 in all 4 positions. Should these be this hot?

The good news is, it sounds very nice, bass is not as punchy, but maybe (?) the caps have get some hours on them. AND the best part, NO HUM!!!

Thanks in advance, Dave

9 answers0 replies

9 Comments

dave.db13

1 gün önce

I noticed the board is marked 230 to 380 volts, so 300 is mid point. I guess at this point I'm just going to play it and keep an eye on the zeners. I also posted on DIY audio, but no one replied. If you ever have one on the bench, could you check the temps? I really appreciate your help with this, thanks! As for the rest of the build, I installed the mundorf's, EH7025 tubes, and your list of parts. Only deviation was the power supply caps, and transformer.

Skunkie

1 gün önce

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Replying to

It's 230V to 280V. And next one I build I will power it up out of the box and check the temps.

dave.db13

1 gün önce

Replying to

That would be great, let me know what temp you find. I double checked, this board is printed 230 to 380 volts. Thanks!

Skunkie

16sa.

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Replying to

Not trying to be argumentative, but that's a misprint if it says that or it's a different board than the ones I have used. I have 5 of them here and they all say 230-280V and the OG schematic shows 250V. I know bleeding off excess voltage can create heat.

dave.db13

2 gün önce

Measured 300 VAC into board. Also using choke in place of the 1K 3 watt resistor.

Skunkie

2 gün önce

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Replying to

The 300V input might be why you are seeing some extra heat? But honestly, I've never measured the temp of those parts so that's a guess. I also found your comment about the bass being weak odd, These as build by me sound very punchy on the low end, if anything a little extra bass. But not sure what caps etc you used as you were also changing other parts from my build of this board.

Skunkie

2 gün önce

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What is the AC input voltages to the board?

dave.db13

May 05

Power supply filter 100uF caps were increased to 330 and 220uF. The 22uF caps were increased to 47uf. Everything else installed is the value indicated on board. I double checked to make sure power supply resistors are in correct spot. There is a notation on the board of 285 volts, and I measure exactly 285 at that spot. Several other builders have used 4 5373 zeners, to get voltage closer to spec, which seems to be correct. I have 8 hours on it now, and the heater voltage measured 6.05, up from the first hour. I did check spec sheet for 5373, and operating temp max is 300F. Seems pretty darn hot to me. Glad I spaced these off the board. Thoughts?

Skunkie

May 05

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Never measured them, pretty sure 2 are 5373 and 2 are 5374? Did you change any other values in the pre-amp?