Need hep to repair my SE-9

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Lux Man

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Need hep to repair my SE-9
« on: 19 Mar 2014, 03:16 am »
I recently acquired a non-working SE-9. Is there someone who wouldn't mind to much to provide me some information. Mainly a picture of the bottom of the board to be sure the previous owner didn't mess something up and maybe a few voltages? It would be a huge help otherwise how do you contact Norh? My emails bounce back immediately.

jqp

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Re: Need hep to repair my SE-9
« Reply #1 on: 20 Mar 2014, 12:56 am »

Lux Man

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Re: Need hep to repair my SE-9
« Reply #2 on: 20 Mar 2014, 03:39 am »
I have read through all the past threads regarding this amp but I didn't find any of much help. I suspect unless someone still has one that's working I may be in tough shape on this one.

jqp

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Re: Need hep to repair my SE-9
« Reply #3 on: 21 Mar 2014, 04:58 am »
How did you pick this up? I have inquired about any SE-9 info via personal channels, but not sure what info I can get.

Lux Man

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Re: Need hep to repair my SE-9
« Reply #4 on: 27 Mar 2014, 07:38 pm »
I looked high and low to find useful info. on this amp and found very little. I am also a member at Audiokarma.org where I began a thread prior to this one. If you want to see the results go to http://www.audiokarma.org/forums/showthread.php?t=581965&page=2 I was successful in getting this amp back into playing condition. Pretty challenging at times without a schematic but I believe it was well worth it. I ended up paying someone to help me who had a variac as well as some other test equipment that I don't have.

I hope that including the link to another forum is not a violation of Audiocircle's rules, it is just so much easier this way.

jqp

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Re: Need hep to repair my SE-9
« Reply #5 on: 28 Mar 2014, 02:16 am »
I think that is fine. Thanks for posting more info that you have found.

I will take the liberty to summarize:

"The sequence for the fuse blowing is this: I plug it in- 10-15 seconds later the tube arcs and the fuse flashes."

"It took 6 hrs. on the bench with a tech but by 11:30 last night is was working at last.

I won't bore you too many details but for the sake of some future Norh SE-9 owner I'll leave a few. The problem was the choke after all. Here was the curve ball. The power supply with the choke in it functioned perfectly when the supply was isolated from the rest of the circuit but as soon as we connected the rest of the circuit the current ran away. We wrongfully assumed the problem was in the rest of the circuit. It was in the power supply- it was the choke. It turned out one side of the choke was shorted to it's mounting frame somewhere somehow, therefore when we connected it to the rest of the circuit it completed a virtual dead short to ground thru the B+ line. We removed the choke and we were listening to test tones in 10 minutes.

As a side note we would recommend a few mods to this amp which I will be doing. The choke is only about 1H. we believe 3-5 would be much better. The power supply cap is a single 100uf 450V I'll be adding in another 100uf. I'll also be recapping it with low esr Panasonics. Possibly more importantly the power being dissipated by the EL 34's was in the 23-25 watt range, which is too much. As a temporary fix we put it a lower output rectifier tube but I'll be adjusting the cathode resistors to bring down the current so I can use the 5AR4 agian and run the EL34's closer to their full potential. The cathode resistor is the 390ohm so I'll use something closer to 450."

Your friend said:
"Ahhh, the choke! Rare!

I personally have not seen a choke problem in hundreds of amplifiers that have come through my fingers."

Really really good info for other SE-9 owners.

My understanding is that these wonderful amps were not actually manufactured by nOrh, but they sourced (Chinese?) and marketed them. Keep us up to date with any successful mods you may do!

Lux Man

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Re: Need hep to repair my SE-9
« Reply #6 on: 28 Mar 2014, 07:48 pm »
I will post again because there will be a few more mods than I listed above. This should actually be a very very nice little amp when it is finished. I suspect it will be a couple of weeks yet since I need to wait for parts to come in.

HarleyMYK

Re: Need hep to repair my SE-9
« Reply #7 on: 14 Apr 2014, 05:11 am »
I don't know if this is relevant, but on my SE-9, when the 12AX7 goes, the fuse blows.  Replace the 12AX7 and fuse and all is well.  This happened at least twice in the eight or so years that I was running it daily or continuously.