Cornet2 pics but doesn't work

leitmo · « **Reply #40 on:** 29 Oct 2008, 01:34 pm »

thanks for sharing your knowledge!

i'm quite sure resistors are correctly installed, Jim made it work when i returned it back so the most probably is tube damaged during shipping.

i noticed Jim connected output wires to R222L and R222R, i suppose he did it for minimize hum,

i'll post voltages as soon as possible!!!

leitmo · « **Reply #41 on:** 30 Oct 2008, 02:21 pm »

So, i changed 12AU7, both tubes are not brand new but i don't believe both are damaged,here are the results:
Voltages were measured on both sides of resistors, it's marked as OUTER (resistor lead nearer to edge of PCB) and INNER (resistor lead nearer to center of PCB), sorry if some terms are wrong in english, i must confess i'm Spanish

LEFT CHANNEL:
- R215: outer 3'75 - inner 5'78
- R217: outer 3'05 - inner 3'29
As you can see in PCB R218 is mounted vertically so there is no OUTER or INNER side, just UP and DOWN
- R218: up 0 - down 3'03

RIGHT CHANNEL:
- R215: outer 4'30 - inner 5'76
- R217: outer 3'65 - inner 4'23
- R218: up 3'73 - down 0

i also tested following resistors on both channels: R215, R216, R217, R218 and R219 and values are OK.

i found interesting that "R218L up" voltage is the same as "R218R down" and "R218L down" is near the same as "R218R up"

any suggestion will be welcome!

leitmo · « **Reply #42 on:** 5 Nov 2008, 07:42 pm »

Hi everyone! (hope someone still there...)

i replaced 12AU7 for a brand new and checked resistors and capacitors you see below,

resistors have been checked and there's no bad one

i know it's a long and painful thread but i only want to share with you my finished cornet2

any suggestion will be welcome!!!

amandarae · « **Reply #43 on:** 7 Nov 2008, 06:50 am »

HELLO,

Something is really odd here.

1.) Can you please measure the voltage( DC) at C106 with respect to ground. Also, at R104 with respect to ground.
2.) Can you please measure the the AC voltage at C102 with respect to ground.
3.) At one end of R215, you should see close to 6.2 Vdc. If not, you go backwards from there up to C209.

I think your problem is the filament supply.

regards,

Abe

leitmo · « **Reply #44 on:** 7 Nov 2008, 08:57 am »

thanks for your reply amandarae!

i'll leave the library in 3, 2, 1... and check Cornet2

i'll post results as soon as possible

Regards!

leitmo · « **Reply #45 on:** 8 Nov 2008, 09:17 pm »

here are the results:

1) DC voltage at C106 respect to ground: 7'65
DC voltage at R104 respect to ground: 7'55 (outer side), 3'89 (inner side)

2) AC voltage at C102 respect to ground: 3'82 (outer side), 3'75 (inner side)

3) at R215 i measure 5'91 VDC, Jim replied maybe changing some resistors i could increase voltage to 6'2 VDC

now it's 10'36pm here, so i'll check components from R215 to C209

Thanks for the patient!!!

amandarae · « **Reply #46 on:** 14 Nov 2008, 02:28 am »

Quote from: leitmo on 8 Nov 2008, 09:17 pm

here are the results:

1) DC voltage at C106 respect to ground: 7'65
DC voltage at R104 respect to ground: 7'55 (outer side), 3'89 (inner side)

2) AC voltage at C102 respect to ground: 3'82 (outer side), 3'75 (inner side)

3) at R215 i measure 5'91 VDC, Jim replied maybe changing some resistors i could increase voltage to 6'2 VDC

now it's 10'36pm here, so i'll check components from R215 to C209

Thanks for the patient!!!

Hello,

I think the heater, although a little bit lower, is fine unless you cannot measure anything at C205 with respect to ground. My problem is that at R219/R217 junction, why are you measuring a very low dc voltage? Looking at the schematic, one end of R219 (connected to C208) is about 150 Vdc while the other should be approximately more than 150 Vdc. if everything is working fine.

My hunch is that the problem is on the Q200 transistor for both channels.

regards,

Abe

leitmo · « **Reply #47 on:** 4 Dec 2008, 02:39 pm »

Hi amandarae and all!

sorry for late reply, i still have not changed Q200, i think (and hope) you're right but it's so strange both Q200 are wrong, maybe one of them would break but both...it makes me think if breakdown comes before Q200

damaged transformer?? but it has no sense if Jim tested OK when sent it back, isn't it?

i'll order some Q200 and try them

Regards!!!

hagtech · « **Reply #48 on:** 5 Dec 2008, 07:23 am »

I don't think it is the transistors. Did you re-wire the inputs, or try them as I had left them? Unit was working fine here, but I made huge changes to the chassis wiring. The original problem was not a bad component, but too much hum pickup on the inputs - resulting in hundreds of volts of swing at the output - thereby saturating the collectors of the transistors. The problem was purely noise.

jh

leitmo · « **Reply #49 on:** 5 Dec 2008, 05:17 pm »

Hi Jim,

i only changed transformer input wires from 120 to 230V, only this. Input/output wires

As you wrote, you sent it tested OK that's why i'm thinking about damaged transformer...

i read somewhere there must be no AC voltage at R223, i'll measure and post results

mysteries...

leitmo · « **Reply #50 on:** 10 Dec 2008, 06:07 pm »

any clue?

could it be transformer??

hagtech · « **Reply #51 on:** 11 Dec 2008, 07:19 am »

I don't think transformer. Are you getting the proper dc voltages for the various supplies?

jh

leitmo · « **Reply #52 on:** 11 Dec 2008, 08:51 pm »

hi Jim, when say "dc voltages for the various supplies" are you referring to voltage points marked on PCB?

sorry i didn't understand it

hagtech · « **Reply #53 on:** 12 Dec 2008, 02:24 am »

Quote

are you referring to voltage points marked on PCB?

Yes. But do the ac side first. It sounds like that is where the problem is.

jh

leitmo · « **Reply #54 on:** 14 Dec 2008, 12:54 pm »

ok jim! i'll check ac ASAP, maybe 120V wiring is correct and 230V primary is wrong...who knows??

thanks for the patient!!!

leitmo · « **Reply #55 on:** 17 Dec 2008, 11:09 am »

Hi!

i've checked AC voltages on secondary of transformer, all measures were taken between secondary wires and GROUND. Primary was connected to 220VAC:

- GREEN 1: 120VAC
- GREEN 2: 120VAC
- RED 1: 39VAC
- RED 2: 177VAC
- YELLOW 1: 103VAC
- YELLOW 2: 102VAC
- GREEN/YELLOW: 119VAC
- VIOLET: 49VAC
- YELLOW/BLACK: 102VAC
- YELLOW/RED: 66VAC

and i also measured voltage between RED 1 and RED 2, YELLOW 1 and YELLOW 2... don't know if it's useful:
- GREEN 1 AND GREEN 2: 3VAC
- RED 1 AND GREEN 2: 604VAC
- YELLOW 1 AND YELLOW 2: 1VAC

anything wrong?

hagtech · « **Reply #56 on:** 21 Dec 2008, 06:03 pm »

Yellow 1 and 2 should be 5Vac. This is the filament for high voltage rectifier. Without it no B+ voltages. Could be a shorted tube? Remove the rectifier and measure again. If 5Vac, then tube is bad. If it stays at 1Vac, then shorted winding in tranny. Maybe the result of overheating?

jh

leitmo · « **Reply #57 on:** 22 Dec 2008, 03:44 pm »

i measured all this voltages with secondary wires disconnected from PCB, wires were "floating" so no tubes were involved.

leitmo · « **Reply #58 on:** 22 Dec 2008, 03:45 pm »

may i suppose tranny is bad??

hagtech · « **Reply #59 on:** 27 Dec 2008, 03:56 am »

Check again on the output side. Never mind ground. Just measure ac between RR, YY, GG (3 separate readings). Is primary strapped for 120V or 240V?

jh