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February 24, 2020, 04:31:43 PM

Author Topic: Failed conversion to 45s  (Read 832 times)

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Offline jake111

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Failed conversion to 45s
« on: January 31, 2017, 06:32:31 AM »
I think I fried my Stereomour trying to convert it to 45s.
-Removed the 5W 360R resistors from the PC board
-Removed the 5W 4.7K cathode resistors
-Swapped both of the HV+ black/red striped wires to the red wires coming from the plate choke
-Left the blue plate choke wires on A2 C2
This amp is one of the prototypes.
The resistance check was good. The voltage check is horrible and the LEDs are out.

I wanted to check with y'all to see if I did the conversion correctly before I posted the voltage check.
Thanks, Jess

Offline maryc27182

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Re: Failed conversion to 45s
« Reply #1 on: January 31, 2017, 04:44:16 PM »
Hi Jess, it's been a while since I did the conversion, but a brief check of my manual (and there was a post regarding the plate choke wires, but it looks like you knew about that) seems to confirm what you wrote.
DIY 2-ways (TAD TD-2002, AE TD15M), Stereomour 45
Fostex TH-500RP, S.E.X. 2.1
Eros Phono

Offline jake111

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Re: Failed conversion to 45s
« Reply #2 on: January 31, 2017, 06:01:30 PM »
Ok, sounds like I wired it correctly. Here's the voltage check:
 Line voltage is 124.4v
* means the meter is ranging around
  Mine       Spec.
1.  441v    340v
2.  439v    165-220v
3.  0          0
4.  0*         0
5.  0          57v
6.  0          0
7.  0          0
8.  0          0
9.  0          0
10. 0         0
11. 0*       57v
12. 0         0
13. 0         0
14. 439v    165-220v
15. 0         340v
16. 0*       57v
17. 445v    350v
18. 0         0
19. 440v    350v
20. 0         57v

A1. 0*       57v
A2. 443v   320v
A3. 0        0
A4. 0        57v

C1. 0*      57v
C2. 444v  320v
C3. 0       0
C4. 0       57v

IA. *       350v
IB. *       350v
OA. *      165-220v
OB. *      165-220v

kreg. *    2.5v
-reg. 0     0

A1-A4 2.68acv
C1-C4 2.67acv

Offline Paul Birkeland

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Re: Failed conversion to 45s
« Reply #3 on: February 01, 2017, 06:19:25 AM »
Neither tube is conducting, at all.  Put your 2A3's in instead of the 45's and see if the voltages come up.  Whatever happened, it is affecting both channels, or you potentially have two dud tubes (can you see the filaments lighting?).
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline jake111

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Re: Failed conversion to 45s
« Reply #4 on: February 02, 2017, 08:21:36 AM »
Well I'm embarrassed, I didn't put the tubes in.
Everything checks out and it sounds great. I might try some EML 45s.
Thanks for the help. Jess