Question regarding 7199 Tube wiring

devilsindetails · 06:18 AM

A friend brought in an old console stereo SE power amp he retrofitted with a 500k dual gang volume pot and a pair of RCA signal input cables.

The amp utilizes a pair of 7199 tubes feeding a pair of 7408 (6v6 variant) output tubes.

He had the vol pot inputs 1 and 2 going to their respective positive L and R RCA signal input wires.

And he wired volume pot wiper 1 to Pin 9 of one 7199 tube and wiper 2 to Pin 9 of the other 7199 (which according to my pin-out chart for this tube are the grids for the Triode portion of this tube)

The grounds from the volume pot run back to the common chassis ground at the signal input grounds of L and R RCA inputs.

The problem is that although the amp produces output the signal shows minimal increase in gain then max at about the 1/4 position and remains constant from the 1/2 position to 3/4 position and then cuts out completely at the max position.

I disconnected the volume pot from the amp while feeding it a signal from a CD player with variable output and all is well. Amp sounds great and performs as it should.

Checked the resistance of the pot and it too checks out at 478 ohms - 0.

My question is that I notice the 7199 tubes in this amp are bridged between pins 2 (Pentode plate) and pins 7 (Triode Grids). Does this seem correct?

If it is...then where exactly does one run the wires from Wipers 1 and 2 from the volume pot to on the 7199s in order to properly implement a volume pot?

Thanks. Leon

SY · 5th February 2013, 09:46 AM

The wipers need to go to the grids of the pentodes. The plate is directly coupled to the triode grid, which you should leave alone.

See the RCA tube manual for schematics of this very common arrangement.

Tom Bavis · 5th February 2013, 01:07 PM

Single-ended amp with 7199? Only one I know is the Stromberg Carlson ASR-110. If that's it, see my page for a schematic: Made In Rochester

devilsindetails · 02:05 PM

Thanks gentlemen...that clears up the matter...I really only have a little experience with 12A_7 variety pre-amp stages so the wiiring of the vol pot on this kind of threw me...

Yes...I checked with my friend and it did, indeed, come from a Stromberg Carlson console of some kind....thanks again, Leon

5th February 2013, 06:11 AM	#1
devilsindetails diyAudio Member Join Date: May 2011 Location: 100th Meridian	Question regarding 7199 Tube wiring A friend brought in an old console stereo SE power amp he retrofitted with a 500k dual gang volume pot and a pair of RCA signal input cables. The amp utilizes a pair of 7199 tubes feeding a pair of 7408 (6v6 variant) output tubes. He had the vol pot inputs 1 and 2 going to their respective positive L and R RCA signal input wires. And he wired volume pot wiper 1 to Pin 9 of one 7199 tube and wiper 2 to Pin 9 of the other 7199 (which according to my pin-out chart for this tube are the grids for the Triode portion of this tube) The grounds from the volume pot run back to the common chassis ground at the signal input grounds of L and R RCA inputs. The problem is that although the amp produces output the signal shows minimal increase in gain then max at about the 1/4 position and remains constant from the 1/2 position to 3/4 position and then cuts out completely at the max position. I disconnected the volume pot from the amp while feeding it a signal from a CD player with variable output and all is well. Amp sounds great and performs as it should. Checked the resistance of the pot and it too checks out at 478 ohms - 0. My question is that I notice the 7199 tubes in this amp are bridged between pins 2 (Pentode plate) and pins 7 (Triode Grids). Does this seem correct? If it is...then where exactly does one run the wires from Wipers 1 and 2 from the volume pot to on the 7199s in order to properly implement a volume pot? Thanks. Leon __________________ I have yet to see any problem, however complicated, which, when you looked at it in the right way, did not become still more complicated. (Poul Anderson) Last edited by devilsindetails; 5th February 2013 at 06:18 AM.

5th February 2013, 09:46 AM	#2
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	The wipers need to go to the grids of the pentodes. The plate is directly coupled to the triode grid, which you should leave alone. See the RCA tube manual for schematics of this very common arrangement. __________________ If there's a sucker born every minute, where do the rest of them come from?

5th February 2013, 01:56 PM	#4
devilsindetails diyAudio Member Join Date: May 2011 Location: 100th Meridian	Thanks gentlemen...that clears up the matter...I really only have a little experience with 12A_7 variety pre-amp stages so the wiiring of the vol pot on this kind of threw me... Yes...I checked with my friend and it did, indeed, come from a Stromberg Carlson console of some kind....thanks again, Leon __________________ I have yet to see any problem, however complicated, which, when you looked at it in the right way, did not become still more complicated. (Poul Anderson) Last edited by devilsindetails; 5th February 2013 at 02:05 PM.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
7199 replacement in AMPEX 6973	pwdiya12	Tubes / Valves	6	18th August 2012 01:58 AM
ECF80 instead of 7199	richwalters	Tubes / Valves	22	27th December 2011 12:55 AM
7199 RCA AND GE tubes	Original Burnedfingers	Swap Meet	2	19th May 2009 11:02 AM
How long does a 7199 last?	gnugear	Tubes / Valves	3	11th August 2005 06:45 AM
7199 glowing purple?	GLF	Tubes / Valves	10	17th February 2003 11:08 PM


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

5th February 2013, 01:07 PM	#3
Tom Bavis diyAudio Member Join Date: Jun 2002 Location: Macedon NY	Single-ended amp with 7199? Only one I know is the Stromberg Carlson ASR-110. If that's it, see my page for a schematic: Made In Rochester

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read