SE9 problem - suggestions requested

Bhasi · « **on:** 4 Aug 2003, 03:54 pm »

My beloved, one year-old, SE9 has just come out of a period of enforced storage, during which it was boxed but - I fear - on its side, only to have developed left-channel distortion.

Swapping speaker connections around has confirmed it's the amp that's got the problem and swapping the paired valves/tubes shows it's not going to be as simple as I hoped to rectify. Talking of which, could it be the rectifier?

Gingerly removing the base-plate left me none the wiser - nothing loose or damaged-looking.

Before I fork out serious (London, UK) money to have it looked at professionally, has anyone got any suggestions as to what it might be?

(The sound is very distorted through the left channel: lower in volume, 'hoarse' at higher pitches.)

Thanks in advance.

jackman · « **Reply #1 on:** 4 Aug 2003, 04:13 pm »

Switch the tubes to see if you have a damaged tube. If that's the case, you are a lucky man. First switch the preamp tubes, then the power amp tubes. Also, try the rectifier. It's a cheap way to see if the amp is damaged because those tubes are inexpensive.

J

Bhasi · « **Reply #2 on:** 4 Aug 2003, 07:42 pm »

Jackman

Thanks for taking the time to reply.

My second paragraph (above) has me doing exactly what you suggest but in vain, and wondering about the (single) rectifier. Is it worth getting a new one to check? Could it affect just one channel?

jqp · « **Reply #3 on:** 4 Aug 2003, 08:36 pm »

Glad you're getting to unpack the SE9, sorry it isn't going smoothly

I would suspect any tubes first, then sockets, then possibly loose wires inside. I assume no one "demo" the SE9 while it was in storage!

KevinW · « **Reply #4 on:** 4 Aug 2003, 09:55 pm »

It's definitely not the rectifier. I can't think how being stored on its side would cause any damage. However if it took any sharp knowcks, you could have a damaged output transformer. I've had similar problems. The only way to verify this, if there's no obvious loose wires or connection on the inside, would be with a scope and signal generator.

Bhasi · « **Reply #5 on:** 5 Aug 2003, 08:44 am »

jqp, Kevin W

Thanks for your input. I'm pretty certain there were no knocks or unauthorised demo-ing, so I think it's probably beyond quick (home) fixes. I'll try it again when I get back from holiday in a fortnight (ever the optimist!) and then, if necessary, get it looked at professionally.

By the way, on the subject of safety, I've heard that capacitors can discharge slowly and can store potentially lethal voltages (or do I mean currents?), so what are the rules to follow? I've been switching off for several hours and then disconnecting from the mains overnight before swapping tubes, but I suspect that's overdoing it.

Gbatokai · « **Reply #6 on:** 5 Aug 2003, 09:12 am »

The largest capacitors in the SE 9 are the two found in the power supply, rated at 100uF@450V, which is not that much, really.

You can safely swap tubes after turning the SE-9 off, waiting 10-30 seconds for the amp to run down. The tubes do get hot, though, so beware

There are only a few volts across the power supply caps a couple of minutes after shutdown, so waiting 10 minutes before opening the chassis should keep you in the clear. If you are still concerned, buy a 10 ohm, 10 watt resistor, and discharge the capacitors manually after having opened the case.

I'm not very adept at electronics, though, so I take no responsibility - although I have done some modifications to the SE 9 without gettin electrocuted.

Bhasi · « **Reply #7 on:** 5 Aug 2003, 11:49 am »

Gbatokai

Thanks for this. I won't be doing more than swapping tubes again, so hopefully I'll stay out of danger!

KevinW · « **Reply #8 on:** 5 Aug 2003, 02:36 pm »

Quote from: Bhasi

jqp, Kevin W

Thanks for your input. I'm pretty certain there were no knocks or unauthorised demo-ing, so I think it's probably beyond quick (home) fixes. I'll try it again when I get back from holiday in a fortnight (ever the optimist!) and then, if necessary, get it looked at professionally.

By the way, on the subject of safety, I've heard that capacitors can discharge slowly and can store potentially lethal voltages (or do I mean currents?), so what are the rules to follow? I've been switching of ...

whoah! THat's overkill as far as tubes are concerned. As long as the amp is turned off, you can switch tubes at will, although hot tube is slightly more fragile than a cold one.

Regarding the caps on the inside... you DO need to be very careful as they store a lot of energy (voltage times current). Depending on the quality of the cap, it can maintain that energy for days or weeks. The blackgates I used to upgrade my SET amp need to be discharged with a special jumper that has a 5watt 500 Ohm resister soldered into the middle.

Now with the SE9, I doubt there are any black gates in there (they cost too much for the price). The caps probably discharge themselves overnight. Here's what I would do... flip the power switch off while music is still playing into the amp. This will help discharge the energy in the power supply caps. Use a voltmeter to check the voltage on the caps. If it's more than 25 volts, don't risk putting your fingers in there. Or at the least, use only on hand at a time, and make sure you don't touch anything near the PS AND that you are wearing rubber soled shoes for insulation

PM me if you need any more advice on troubleshooting.

starlet · « **Reply #9 on:** 5 Aug 2003, 02:45 pm »

Bhasi, did you contact Michale? Maybe he can help you fix it without spending a lot of $$.?

Bhasi · « **Reply #10 on:** 5 Aug 2003, 08:56 pm »

Starlet

Good idea, but I hesitate to trouble Michael with this directly as, anyway, he's listed as the facilitator of this forum and I expect he'll chip in if any of the very constructive contributors to this thread miss anything out.

Bhasi · « **Reply #11 on:** 5 Aug 2003, 09:06 pm »

Another observation:

When I power the amp down with music still playing, the distorted channel fades out much quicker than the good one. Does that suggest anything to anyone?

The Yellow Pages beckon, I fear!

KevinW · « **Reply #12 on:** 5 Aug 2003, 09:29 pm »

Unfortunately that doesn't really mean much. The only way to know is with an osciloscope and signal generator to trace the point where the problem occurs in the circuit. Yellow pages it is, and good luck.

If I was forced to guess, I would say that points to an output transformer problem, which would be expensive and difficult to replace, although not impossible.

Bhasi · « **Reply #13 on:** 6 Aug 2003, 05:56 am »

Thanks to everyone here for their suggestions.

I've located a competent-sounding engineer north of London via an ad in HI-Fi World magazine (UK) and will report back next month when I've had the amp looked at.

(I'll be a happier man when I can return my SS Pioneer A400 to the retirement it deserved!)

mbarnes · « **Reply #14 on:** 6 Aug 2003, 04:23 pm »

It sounds like a tube to me. I would think it is one of the 12AX7s. These are very inexpensive to replace. Try swapping first.

I can not imagine a capacitor going bad by just sitting around. If it did go bad, it would have some physical signs. These are fairly easy to replace as well.

wunderlast · « **Reply #15 on:** 8 Aug 2003, 05:44 pm »

Electrolytic capacitors are famous for going bad because they aren't being used. HOWEVER, it usually takes years for this to happen.

Bhasi · « **Reply #16 on:** 21 Oct 2003, 01:30 pm »

A belated up-date for anyone interested:

nOrh replaced the SE9 as it was within warranty when the fault developed. The new one works perfectly and I'm delighted - again - with its ability to handle all kinds of music and its obvious synergy with the SM 6.1s. The addition of an ACA 2b is back on my upgrade agenda, but not urgently. (If ONLY it had RC!)

By the way, nOrh's service in this case has been good, but EU residents and others subject to import duties (even on replacement items, apparently, in the UK) should note that the company's goodwill does not extend to covering your losses in that respect. Fortunately, nOrh's prices are low enough to begin with to help cushion such misfortunes!