Pow_22 Posted November 11, 2011 Share Posted November 11, 2011 (edited) Ive had my B120 for around a year now and its time it went in for a service. I think the tubes are original so im preparing for the news that they need replacing. Ive had a look at the usual suspects (Hot Rox and Watford Valves) to see how much i can get a set for to get fitted should the Mullards be pronounced DOA. I think i might have a little go at changing the pre-amp valves using Mr Foxens build diary as a guide. WHen i look through the top vent i can see a glow from 2 but not the others (maybe in a shielding can?) So i think thats me needing 1 x 12AT7 and 4 x 12AX7 plus obviously the 6 x EL34 power valves (how much glass!!!!) Recently the amp is a little 'farty' at first but once fully warmed up (maybe 10-15 mins of full playing) it does get better. Looking at the amp i dont think the thing has ever even been opened up so it could be an expensive service. Just debating over whether to take it to Dave Lunt (highly recommended but a few horror stories) or David Pye in Preston (seems well recommended and fairly cheap). Anyway, i know there are a few SC guys on here so anyone recommend a good Valve supplier incase the worst happens Edited November 11, 2011 by Pow_22 Quote Link to comment Share on other sites More sharing options...
Mr. Foxen Posted November 11, 2011 Share Posted November 11, 2011 I'm prob gonna order pile of valves from Hong Kong soonish, if you aren't in a rush. Have 6EL34 sat here from last lot I ordered if you are in a rush. Ordering overseas is pretty much the way, the current production Shuguangs are very good. Recap isn't a bad plan. Quote Link to comment Share on other sites More sharing options...
Twigman Posted November 11, 2011 Share Posted November 11, 2011 I know very little about valves. While my HA3500 was open the other day I spotted there was a 12AX7 in the preamp circuit.... It seems to have a very high noise floor (compared to SS amps) and I was wondering if changing the valve might lower this noise floor so I get less hiss at higher tube-pre volumes? Are all 12AX7 valves the same? Will any 12AX7 valve plug'n'play? Is it as simple as changing a lightbulb or is there soldering required? 'scuse the ignorant questions Quote Link to comment Share on other sites More sharing options...
Mr. Foxen Posted November 11, 2011 Share Posted November 11, 2011 12aX7 are light bulb easy. A good one might help hiss. Quote Link to comment Share on other sites More sharing options...
Pow_22 Posted November 12, 2011 Author Share Posted November 12, 2011 cheers Oli, in no big rush,wont be goin to the tech till after payday. Ive never even taken the chassis out the box so who knows what lurks in there. Just thought i could at least try chaging the pre-valves as i know they are fairly easy. Will give you a shout re: the valves. Cheers Quote Link to comment Share on other sites More sharing options...
BassHertz Posted November 15, 2011 Share Posted November 15, 2011 If it has never been opened/serviced I would also budget for a change of power supply reservoir capacitors and the cathode bypass electrolytic capacitors. i recently overhauled a Simms Watts PA200 - i got my capacitors from here [url="http://www.audiocap.co.uk/ft-capacitors-2-c.asp"]http://www.audiocap.co.uk/ft-capacitors-2-c.asp[/url] Quote Link to comment Share on other sites More sharing options...
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