SG505 puzzle

jackinnj · 27th August 2006, 10:26 PM

my Textronix SG505 had been operating as close to perfectly as one could imagine until this afternoon -- now we have some 120Hz problems -- has anyone ever had the internal +/- 15 V regulation system on this thing go wonky?

anatech · 27th August 2006, 10:31 PM

Hi jackinnj,
Like everything else, yes. How old did you say they were?

The repair is very straight forward and unlikely to affect the calibration, unless the 120 Hz residual was not found at the time of it's last cal.

-Chris

Edit: check your rack / supply also.

jackinnj · 28th August 2006, 12:25 AM

yeah, I will check the pass transistors on the TM5006 before I start screwing around with the SG505 -- I had looked at the residuals back in the early summer and it wasn't a problem at that time so it must be the mainframe. the SG505 was yielding THD of 0.0005% to 0.0008% back at the time I did the article on the Super Oscillator.

the TEK mainframe is on almost all the time.

anatech · 28th August 2006, 12:32 AM

Hi jackinnj,
At least you have a simple problem!

-Chris

jackinnj · 28th August 2006, 03:36 PM

fwiw -- here's the power supply regulator used in the SG505 -- Q2 and Q3 are located in the TM5006 chasis:

anatech · 28th August 2006, 09:22 PM

Hi jackinnj,
Did you find the fault?

Wishing you success ......

-Chris

jackinnj · 28th August 2006, 11:09 PM

yes, it was the F29555, F30555 pass transistors -- insulated TO-220 versions of the ubiquitous power supply transistors. I also gave the TM5006 a good airing with the compressor.

anatech · 29th August 2006, 12:01 AM

Both?
Interesting.

jackinnj · 29th August 2006, 01:11 AM

I didn't bother to check -- the SG505 worked well in all the other bays -- for the moment I have replaced the 2955/3055 with another On-Semi device of which I have thousands.

I have an SG502 which is completely dead -- some of the physical construction is identical to the SG505 but the 502 dates from 1971 -- this could be an interesting fixer-upper.

anatech · 29th August 2006, 01:16 AM

I have a couple Tek modules but no rack. Would you sell your 502? I don't mind fixer upper.

-Chris

27th August 2006, 10:26 PM	#1
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	SG505 puzzle my Textronix SG505 had been operating as close to perfectly as one could imagine until this afternoon -- now we have some 120Hz problems -- has anyone ever had the internal +/- 15 V regulation system on this thing go wonky?

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
SG505 schematic	GK	Solid State	2	2nd February 2009 11:48 PM
Cordell SigGen vs the HP339 and SG505	jackinnj	Equipment & Tools	3	11th October 2007 05:29 PM
TO3 puzzle	Zen Mod	Parts	2	3rd December 2006 10:45 AM
help me with this puzzle...	AudioGeek	Tubes / Valves	3	21st May 2005 07:48 PM
cd 650 puzzle	guido	Digital Source	12	23rd July 2003 10:29 AM

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


	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

27th August 2006, 10:31 PM	#2
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi jackinnj, Like everything else, yes. How old did you say they were? The repair is very straight forward and unlikely to affect the calibration, unless the 120 Hz residual was not found at the time of it's last cal. -Chris Edit: check your rack / supply also.

28th August 2006, 12:25 AM	#3
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	yeah, I will check the pass transistors on the TM5006 before I start screwing around with the SG505 -- I had looked at the residuals back in the early summer and it wasn't a problem at that time so it must be the mainframe. the SG505 was yielding THD of 0.0005% to 0.0008% back at the time I did the article on the Super Oscillator. the TEK mainframe is on almost all the time.

28th August 2006, 12:32 AM	#4
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi jackinnj, At least you have a simple problem! -Chris

28th August 2006, 03:36 PM	#5
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	fwiw -- here's the power supply regulator used in the SG505 -- Q2 and Q3 are located in the TM5006 chasis:

28th August 2006, 09:22 PM	#6
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi jackinnj, Did you find the fault? Wishing you success ...... -Chris

28th August 2006, 11:09 PM	#7
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	yes, it was the F29555, F30555 pass transistors -- insulated TO-220 versions of the ubiquitous power supply transistors. I also gave the TM5006 a good airing with the compressor.

29th August 2006, 12:01 AM	#8
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Both? Interesting.

29th August 2006, 01:11 AM	#9
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	I didn't bother to check -- the SG505 worked well in all the other bays -- for the moment I have replaced the 2955/3055 with another On-Semi device of which I have thousands. I have an SG502 which is completely dead -- some of the physical construction is identical to the SG505 but the 502 dates from 1971 -- this could be an interesting fixer-upper.

29th August 2006, 01:16 AM	#10
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	I have a couple Tek modules but no rack. Would you sell your 502? I don't mind fixer upper. -Chris

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)