Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: P Batty on November 09, 2011, 10:45:13 pm

Title: 7199 Dilemma - Resolved!
Post by: P Batty on November 09, 2011, 10:45:13 pm

My thrift store find of the day was a Stereo console  with a Dynakit Stereo 70, Dyna PAS preamp, Dyna tuner, and Garrard 4 speed turntable with an Empire 880 cartridge. No speakers, although both baffles had undamaged wheat grill cloth.  I took it home and, much to my surprise, everything worked! The contacts and pots need cleaning, but all components are quiet and hum-free. The only fly in the ointment is that the Stereo 70 is missing one of its pricey 7199 tubes.  Since I only paid $4.99 for the lot, it seems silly to spend 10 times as much for a NOS tube.  There are numerous tubes which can sub with the socket rewired, 6GH8A and 6U8 are the most common- and cheap.  Reading the ST-70 forums and conversion kit manufacturers' sites doesn't seem to give any consensus.  There are tube socket adapters, which, with tubes, are over $60 a pair. Some people think the sub tubes are better, some think they are worse, others say it doesn't matter.  Has anyone does this conversion? I know that a lot of Ampeg's have this problem. I'm not into "ultimate sound" but do like the sound of tube stereo.  

Title: Re: 7199 Dilemma
Post by: jjasilli on November 09, 2011, 11:48:07 pm

I rebuilt some Stromberg Carlson amps for hi-fi.  One for my son is an ASR-444 stereo amp -- 6U8 PI driving 2X 7027 power tubes.  I have three APH-1100 mono blocs each with a 7199 PI driving 2X KT-88's.  Both types of amps sound great. 

Other alternatives:  I think you can re wire a "socket saver" to make your own adapter.  A good vintage, used (not NOS) tube may be cheaper.  That's what I generally use.

Title: Re: 7199 Dilemma
Post by: DummyLoad on November 10, 2011, 12:32:29 am

the stereo 70 is definitely worth a few bucks thrown at it. there are several "mod" PC boards available. e.g. some use all triode, 6AN8, 6U8, 6GH8, etc. keep it stock if you can. recent production 7199s work fine - sovtek discontinued mfg. but lingering stock is still available.

http://www.ebay.com/itm/NEW-6GH8A-STUFFED-BOARD-Dynaco-ST70-Stereo-70-Dyna-Amp-/220874960591?pt=Vintage_Electronics_R2&hash=item336d2c6ecf#ht_500wt_1172 (http://www.ebay.com/itm/NEW-6GH8A-STUFFED-BOARD-Dynaco-ST70-Stereo-70-Dyna-Amp-/220874960591?pt=Vintage_Electronics_R2&hash=item336d2c6ecf#ht_500wt_1172)

--DL

Title: Re: 7199 Dilemma
Post by: ernie_jr on November 10, 2011, 05:12:54 am

I have used 6an8's in place of 7199. cant tell the difference
ernie

Title: Re: 7199 Dilemma
Post by: triode on November 10, 2011, 06:09:29 am

Look at it this way... with the 7199 in it, the amp is worth $300 in terrible condition. If it is rust free with minor pitting on the chassis, its worth $400-$500.

$40 for a 7199 is not too bad. And if you decide to off it, you will get your cash back many times over. A 6GH8A adapter is pricey, unless you want to purchase one of those sockets and DIY. Those may be like $4, plus a cheap tube.

Up to you, but a stock one is worth outrageous cash now (mostly due to the nice iron).

Title: Re: 7199 Dilemma
Post by: P Batty on November 10, 2011, 08:00:01 am

Thanks for your input, everyone.  The amp is in good condition- no rusting or pitting, was properly assembled, and appears to be dead stock. I think I will keep it that way- I'll try to score a used 7199.

Title: Re: 7199 Dilemma
Post by: jjasilli on November 11, 2011, 08:21:53 pm

I'll try to score a used 7199.

Cool!  I look for a reputable eBay seller with lots of tube sales and a high rating, who tests the tubes as good to like new on a transconductance tester, and guarantees them with a right of return.  You might get 2 or more used, quality, vintage tubes for the price of one new production or NOS tube.

Title: Re: 7199 Dilemma
Post by: triode on November 11, 2011, 08:38:19 pm

Or, if you don't have time to waste with fleabay tubes, just get one from this guy.

http://www.kcanostubes.com/search/node/7199 (http://www.kcanostubes.com/search/node/7199)

Very reputable dealer. Pricey? Yes. Guaranteed? Yes.

I am in no way affiliated with KCA.

Title: Re: 7199 Dilemma
Post by: rafe on November 12, 2011, 11:43:13 am

I have two in a hammond, if you are interested PM me,  I'll check out the make on them but I'm pretty sure they are Great Britain branded hammond.

Title: Re: 7199 Dilemma
Post by: eleventeen on November 12, 2011, 11:47:02 am

WOW, great score on the Dynaco. Great amps. Drool!

Title: Re: 7199 Dilemma
Post by: P Batty on November 12, 2011, 03:33:51 pm

Thanks again, everybody! My local music store/repairman, Mr. Mark of Anoka MN, had a new Sovtek 7199 in a dusty box- he let me have it for $15.  It pays to support your local businessman!

Title: Re: 7199 Dilemma
Post by: Willabe on November 12, 2011, 11:18:17 pm

Quote from: P Batty on November 12, 2011, 03:33:51 pm

My local music store/repairman, Mr. Mark of Anoka MN, had a new Sovtek 7199 in a dusty box- he let me have it for $15.  It pays to support your local businessman!

Nice, good for you and him.     :icon_biggrin:


         Brad   

Title: Re: 7199 Dilemma
Post by: P Batty on November 13, 2011, 06:03:35 pm

My Dyna "Stack", the rack was made from the stereo console-  mahogany veneer panels, solid mahogany sides and trim.  I wish I could have gotten it from the owner before the movers gouged it all up, although more usable this way and better airflow!)

(https://lh3.googleusercontent.com/-24OuBWVOtsM/TsBZQOzK3tI/AAAAAAAAIIg/Vwpnop7uqhk/s800/dyna%252520stack.jpg)