Cornet2 has low volts.

rotcoddam · « **on:** 1 Nov 2004, 05:11 am »

Just completed the kit and it sounds great, but the volts read about 20% low. should I be concerned with the low readings and will it affect the sound quality or hurt the unit?

hagtech · « **Reply #1 on:** 1 Nov 2004, 06:07 am »

What is your line voltage coming in? Twenty percent is a bit much, sound will probably start to thin out.

jh

rotcoddam · « **Reply #2 on:** 1 Nov 2004, 01:39 pm »

Voltage is exactly 120.

rotcoddam · « **Reply #3 on:** 1 Nov 2004, 01:59 pm »

I rechecked the voltages with another dvm and they are the same. I'll post the readings when I get back from work. Thanks.

hagtech · « **Reply #4 on:** 1 Nov 2004, 05:24 pm »

Ok, then maybe there are some other issues. Perhaps the transformer primary is not strapped correctly? Maybe the rectifier is old? Maybe some of the resistor values are not correct? Maybe one of the tubes is the wrong type?

Are both the B+ and H+ voltages equally low? Or just one?

jh

Eric H · « **Reply #5 on:** 1 Nov 2004, 09:14 pm »

Both my Clarinet and Cornet 2 voltages (plates of the signal tubes) were about 10V low with 5Y3GT's. I didn't actually check my line voltage but in the past I believe it's been about 121 or 122 VAC. I had a couple good 5AR4's so I tried them and they brought the voltages right up to spec. Eric

rotcoddam · « **Reply #6 on:** 2 Nov 2004, 07:39 am »

Here are the voltages.
r107 340v
r219L 131v
r219R 130v
r212L 124v
r212R 119v
r211L 300v and 273v
r211R 300v and 270v
r204L 121v
r204R 120v
Some of these are within 10%, a few are over 20.
transformer yel/blk current is 18.5mA
I checked all resistors and put tubes on tester. Checked good.
Tranny hooked up ok.
I replaced c103 with a 34uf I had laying around just to make sure it wasn't the cause, but I had no major changes in the voltage. Took it out totally and r107 went down to 304v so I put the original back in.
Also just noticed the led turns green within a half second of turning the unit on.

rotcoddam · « **Reply #7 on:** 2 Nov 2004, 07:43 am »

Sorry I left this out
The h+ is 7.5v

Eric H · « **Reply #8 on:** 2 Nov 2004, 05:39 pm »

Your voltages are lower than mine ever were... but what I notice is your comment about the red light going out quickly. I had the same thing happen with my cornet2 and I initially thought it was because my 5Y3's were directly heated. I believe that the standard for 5Y3's is directly heated, but some are indirect including the sovtek 5Y3 sold by AES...(according to sovtek specs) Anyway, I replaced the 5Y3 with a 5AR4 and that didn't help. I have also replaced the transistors and LED with no effect. Red light barely comes on, if at all... On my clarinet I never put in a 5Y3 and it has worked perfectly - red light for about 12s, then green. One last thing - my cornet2 makes a sort of "clicking" or "smacking" sound about 5 times/second. I can hear it both through the speakers (quietly) and by putting my ear up to the chassis. Have you noticed any such noise? This and the LED are the two issues I still haven't sorted out on my cornet2... Eric

hagtech · « **Reply #9 on:** 2 Nov 2004, 06:00 pm »

Rotcoddam,

Those voltages sound very low. What is your heater voltage (at tubes)?

jh

rotcoddam · « **Reply #10 on:** 3 Nov 2004, 12:13 am »

Jim,
They're 6.0v-

hagtech · « **Reply #11 on:** 3 Nov 2004, 04:22 am »

Hmmm, 6.0V is a little low, but not that much. I would suspect maybe the drop is due to the rectifier. Design was centered around the response of the Sovtek 5Y3. I've found GZ34 and 5AR4 to also work quite well.

Voltages do not have to be perfect. They vary with tubes. In fact, you'll see differences between channels. You're in the OK zone, but pretty low.

jh