NOSValves Posted October 5, 2002 Share Posted October 5, 2002 Tom, Another option is you can order a custom can cap from www.vibroworld.com for about $25 or so. The only thing is it takes about 2 weeks to get them. They go in exactly like the stock ones and look real nice. I use them all the time. Craig Quote Link to comment Share on other sites More sharing options...
Pland Posted October 6, 2002 Share Posted October 6, 2002 Hi Tom, Good question.Normally I'd say yes,like any other preamp source selector,but I'm not looking at the schematic or the amp.Mobile should know. If you think that the set-up looks scary,you should see the number of caps in the control section of a Scott 299.One of the most heroic pains in the *** to replace you can imagine!If you're thinking of changing caps,I probably wouldn't as the amp sounds great with the current set-up.But I absolutely would upgrade the volume control,and I'd use a DAC(Danish Audio Control) from DIY Cable. I've built two Bottlehead Foreplay preamps,and one of the factory upgrades is a resistor based volume control(sweet whispers).The difference is a revelation.Tracking is perfect ,the whole set up is much quieter,and there is as big an improvement in overall sound as changing tubes.Call Kevin at DIY,and discuss it. Best, Pat P.S. You should have enough room under chassis unless the Atoms are bigger than I remember.Xichon's are very small,and are dirt cheap as well. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted October 6, 2002 Share Posted October 6, 2002 Pland, You sure have that 299 control cap procedure down it is a pain in the a$$. The thing is it will net you almost nothing for your trouble. The caps in the control section generally never fail. I did this to my LK-72 and it was a pain and netted me no difference what so ever. In fact I'm almost to the piont in saying that a guy could only replace the 4 coupling caps going to the output tubes on these scott amps and be safe to go reliablility wise. I have never pulled out any of the caps elsewhere in the amp and found them out of tolerance or bad in anyway. I just replace them because it doesn't take long and most likely helps the the tone and detail of the amp by doing it. Craig Quote Link to comment Share on other sites More sharing options...
Pland Posted October 6, 2002 Share Posted October 6, 2002 Craig, I agree.Further(and be real quiet about this one)I've never had a selenium rectifier fail in any Scott I've owned.I've checked them all,and the voltages have been spot on .If the B+ is ok and if the large resistor by the bias supply isn't fried(and the reverse polarity paper electrolytics aren't leaking),the coupling caps will get it done. My local tech is a german guy,and has about 40 Siemens selenium rectifiers,just like the originals in the 299A/B/C.I'd be inclined to use one of these as an original replacement.The voltages are right without stepping it down with resistors,and since the originals have lasted 40 years or so,reliability isn't an issue. Best, Pat Quote Link to comment Share on other sites More sharing options...
mobile homeless Posted October 6, 2002 Share Posted October 6, 2002 Trouble with the DACT rec is I dont think it will fit in the HF-81 if I rememeber correctly. It is a pretty deep attenuator but Pat is correct; sometimes the difference can be astounding. I have a TKD (but it's too $$$) and the step up from a Noble pot was VERY noticable. On the other hand, get the best ALPS you can and I think you would be ok. That being said, I still have my original volume pots in BOTH my EICOs. But the BALANCE is a mess so bypass it - it will be one less mediocre pot in the signal and it does not work well to begin with. Just get the beast working without the hum. Did you plug the unit directly in the wall? Try different power and grounding schemes? IF you mentioned this, I missed it. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted October 6, 2002 Share Posted October 6, 2002 Pat, I'm surpised you havn't had out of tolerance problems with the selenium rectifiers. I litterally havn't found one in all the amps I've did that wasn't putting out 3 to 4 less neg. voltage than required. Heck the 222D I'm working on now was only sending -30 to the 12AX7 heaters after the dropping resistor network -46 straight out of the rectifier a full 10v low. It sounded like dung !! JCturbo's LK-48 amp was about the same sounded horrible when I got it. First thing I checked was the Neg. Voltage and changed the rectifier and the amp woke right up. I do agree that these originals you have a source for sound like a great option. They probably would out last these SS bridge rectifiers. Is this something I could buy from him or you ?? I'd like to score 10 or 20 if so. Craig Quote Link to comment Share on other sites More sharing options...
No Disc Posted October 6, 2002 Share Posted October 6, 2002 The DACT will not fit without the help of a good dremel tool. I remembering considering one and did the measurements. It's a bit too long to fit without some cutting which is why I ditched the idea. I would really like to head the difference, and perahps one day, I'll get brave enough to cut into the poor little EICO. - tb Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted October 6, 2002 Author Share Posted October 6, 2002 Hey guys, I really appreciate all the info and in-depth knowledge bring provided here. I's like to post some results but I've been working 12.5 hr days this last week and I'm taking my son up to see Thomas the Tank Engine (those w/kids will know) and it/he is at Williams, Az near the Grand Canyon. So, I haven't been able to work on it in several days and won't be able to today either. However, I'm looking forward to fixing these grounding issues and reporting results. In other words, real life intrudes. Kelly, I do have it plugged into a power strip, albeit a quality one. Also, on the same circuit and not far away from a dual tube 4ft. flouescent light over the bench in my garage, I'm wondering if it's feeding hash into the circuit ala' Roger Stevens battery charger. I'll look at that volume control deal too. I'll try to see some pics, but the long stem deal makes me wonder. There's already a cut-out in the chassis for the vol pot. Basically, my goal here is to get the thing sharped up and playing well with resaonably priced available components so I can have somebody with real ears evaluate it and start making some prelimninary decisions about the feasibility of reproducing it in some fashion. The part that worries me is the PS/trannies and that that multi-ganged function switch. Along the line several decisions, some marketing based, will need to made about reproducing the appearance, the functionality or both. It sort of appears that the circuitry could be simplified greatly by eliminating the tone controls and all the sort of oddball functions no longer used. But then, what about the knobs that control that stuff? This could impact the final appearance greatly. Lots of things to consider here. Later, Tom Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted October 7, 2002 Author Share Posted October 7, 2002 Craig, sorry, spaced out your req on the Sam's. Email me your PO address, I will make some copies and send. tmoble@earthlink.net Tom Quote Link to comment Share on other sites More sharing options...
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