Anritsu MG3633A signal generator teardown and repair log - Page 1
Forum section: electronics / repair

author: capt bullshot
author_rank: Super Contributor
timestamp: March 20, 2018, 03:02:47 pm
content: So I've started to tear down and repair the loot from the Duesseldorf triphttp://wunderkis.de/mg3633a/index.htmlThis is work in progress, first unit is fixed, two more to go, stay tuned for updates.Some of us might remember DC1MC and me picked up some stuff there:https://www.eevblog.com/forum/buysellwanted/%28deeu%29-group-sale-of-5-anritsu-mg3633a-signalgenerators-%2810-khz-to-2700-mhz%29/

author: capt bullshot
author_rank: Super Contributor
timestamp: March 21, 2018, 02:10:46 pm
content: Update #1:Some more circuit analysis and fault location happened to unit #2, not yet repaired but root cause of malfunction located:http://wunderkis.de/mg3633a/repair2.html

author: DC1MC
author_rank: Super Contributor
timestamp: March 21, 2018, 07:01:39 pm
content: Excellent tear-down and repair detective story, recommended for everybody who wants to see a properly done and documented repair.Also the generator construction is really a wonder of Japanese technology, I had some kind of electrogasm looking at that gold attenuator !!!Keep on the good work,DC1MC

author: capt bullshot
author_rank: Super Contributor
timestamp: March 22, 2018, 11:24:29 am
content: One more update for today:Unit #1 is no more wacky:http://wunderkis.de/mg3633a/repair1.htmlUnit #2 is "undefekt" now:http://wunderkis.de/mg3633a/repair2.htmlUnit #3 is diagnosed:http://wunderkis.de/mg3633a/repair3.htmlTwo out of three, that ain't so bad?

author: DC1MC
author_rank: Super Contributor
timestamp: March 22, 2018, 11:48:47 am
content: Quote from: capt bullshot on March 22, 2018, 11:24:29 amHey capt, are you taking apprentices ? 'Cause my unit is still in need of some love, I can haul it back to you some time for some spiritual healingBut excellent job indeed, done in a very German way!!I have this strange idea, if you mix the outputs of the two guys that are OK, will this become an even higher frequency generator ?And second, less wacky idea, if those guys will be feed in their reference input from a rubidium 10MHz source, will they become some craz stable generators ?Cheers,DC1MC

author: capt bullshot
author_rank: Super Contributor
timestamp: March 22, 2018, 01:52:03 pm
content: I've added some thoughs about the rather subtle cause of the ceasing oscillation within this PLL (refering to repair #2):QuoteI guess that little electrolytic was dried to some extent, and changed its ratio from C to ESR / ESL somewhat. The ESR must have been still low, otherwise there would have been too much damping, but the ESL apparently formed a resonant tank with the paralleled ceramic cap, resonating in the ballpark of 300MHz. This is the low level oscillation that I could observe when the desired 95MHz oscillation ceased. The damping ratio of these concurring tank circuits must have gone critical here, so the parasitic one could take over.I remember Jim Williams warning about paralleling electrolytic and ceramic caps for decoupling purposes (it's written up in one of his famous app notes), just because this tank formedby the high Q ceramic and the electrolytic's ESL could create serious ringing.

author: capt bullshot
author_rank: Super Contributor
timestamp: March 23, 2018, 09:17:24 pm
content: I've done some timenuttery with the two working ones now:Using a simple power splitter, one can add (not mix) the outputs of two signal generators to see the beat frequency on a scope.Both units set to 100MHz, the scope shows about 2Hz - meaning the OCXOs match to 2*10E-8Adjusting one generators frequency to 100MHz - 2.05Hz results in a constant amplitude (meaning the frequencies are the same), resulting to 2.05*10E-8 oscillators.The reference oscillator of the CMU200 is just about the same accuracy - quite nice for about 1992 vintage instruments.I guess, now I need a GPSDO ...

author: capt bullshot
author_rank: Super Contributor
timestamp: April 18, 2018, 06:31:02 pm
content: Update on unit #3:http://wunderkis.de/mg3633a/repair3.htmlShort story: It came to life again, I've replaced some blown up and obsolete components by modern stuff.

author: DC1MC
author_rank: Super Contributor
timestamp: April 18, 2018, 06:50:12 pm
content: Capt, wie immer (as always), an excellent repair job, nicely illustrated and with good and cost effective solutions found.This puts my lazy old a$$ to shame, you've repaired 3 and I was only able to repair the PS of the SA and order a CRT rejuvenator to see if the tube can survive a bit more or it's the LCD time.I definitely have to meet you again or put my behind in movement.Congratulations and keep up the good work,DC1MCP.S. If you need rejuvenate some of your CRTs, I have the professional solution coming.

author: capt bullshot
author_rank: Super Contributor
timestamp: April 18, 2018, 07:11:01 pm
content: That was a pretty quick reply, have you been sitting all the time and waiting for this post?

author: DC1MC
author_rank: Super Contributor
timestamp: April 18, 2018, 07:26:50 pm
content: Quote from: capt bullshot on April 18, 2018, 07:11:01 pmTold you', lazy a$$I was just logging in and looking at the replies to my posts while crunching some toxic blue chips from Kaufland, we probably reach home around the same time.Cheers,DC1MC