Using the entire PS rather than just the transformer?
I also have a (non-functional CRT) Tek545 scope waiting to be parted out (it was purchased cheap with that condition known and I was pondering about converting it into a TekAmp at that time). Just curious, could the whole "regulated" HV supply complex (such as the DC +500V, +350V, +225V, +100V, and -150V(for bias?) outs) be used directly to setup the HV for the different stages of a push-pull amp (after minor voltage drop adjustments), instead of just chopping away the nice looking power transformer only? "~5-10 mV" ripple sounds good, or the regulation methods used in the Tek scopes are known to be undesirable for (hifi) audio amp applications? Thanks.
I also have a (non-functional CRT) Tek545 scope waiting to be parted out (it was purchased cheap with that condition known and I was pondering about converting it into a TekAmp at that time). Just curious, could the whole "regulated" HV supply complex (such as the DC +500V, +350V, +225V, +100V, and -150V(for bias?) outs) be used directly to setup the HV for the different stages of a push-pull amp (after minor voltage drop adjustments), instead of just chopping away the nice looking power transformer only? "~5-10 mV" ripple sounds good, or the regulation methods used in the Tek scopes are known to be undesirable for (hifi) audio amp applications? Thanks.
Hi ! have a look at my OTLs http://retro-forum.com/viewtopic.php?t=13883 with twin 545A xformers 
schematics shown
http://retro-forum.com/viewtopic.php?t=13883
schematics shownhttp://retro-forum.com/viewtopic.php?t=13883
coresta said:... OTLs http://retro-forum.com/viewtopic.php?t=13883 with twin 545A xformers
http://retro-forum.com/viewtopic.php?t=13883
Thanks. I plan to use the ceramic component support pieces as well. Would you care comment a bit on the (audio) performance and stability of the amp (sorry, can't read French) ? Looks like a very nice project (as compared with my simple plan - a heavily B+ regulated everywhere Williamson/Mullard type of PP amp). (PS: The first link is broken).
Hey Tom,
The tranny is marked with "120-120" on it.
I think the 'official' part-number might be 120-120-00.
On a similar note,I think I may have found one!
www.fairradio.com has some Tek parts and stuff.
Pretty cheap too,except I might have to hit the lottery if I actually want it shipped to me tho.. Minor details!
I wonder if they'll ship it flat-rate,I'll have to ask.
Time to start designing a pair of Monster Monoblocks!
The tranny is marked with "120-120" on it.
I think the 'official' part-number might be 120-120-00.
On a similar note,I think I may have found one!
www.fairradio.com has some Tek parts and stuff.
Pretty cheap too,except I might have to hit the lottery if I actually want it shipped to me tho.. Minor details!
I wonder if they'll ship it flat-rate,I'll have to ask.
Time to start designing a pair of Monster Monoblocks!
All of them are 120/344 from 545, 545A and B . Another pair , from scrapped 581 and 585 will be used in the future for a mono 6336A OTL amp . My amps give 50W continuous on 8ohms load , 400 KHz BW , 10 6080WA per channel ( each xformer is heating 5 of them) 8 x 3100uF each rail .. incredible sound on my Altec VOTs , as stated : "the smooth of flamenco dance with the power of a V12 Jaguar engine " Perfect stability with a floating 0v center output (see the schematic) but 160 hours of homework
Perfect stability with a floating 0v center output (see the schematic) but 160 hours of homework
G.Kleinschmidt said:
I hope that this doesn’t mean that you lot are ripping apart those beautiful old Rolls-Royce oscilloscopes.
no
I still have a 581, 585A, 545A, 551 (dual beam / separate PSU) , two other "memory" , a 5000 series with 4+2 channels .... all working Those i brake were purchased 15 years ago (10 bucks each ) from a scrapper who had 150 UNITS for sale Attachments
![tekscopes [640x480].jpg](/community/data/attachments/85/85939-38f1aef5e5f34ad80f018f947da1cb26.jpg)
Okay,so I did a quick-N-dirty load test on this Tek 120-120 trans..
I grabbed a few lightbulbs,and used them as loads. a 40W a 60W and a 100W,all were 120V bulbs,made by "GE".
(I only tested 2 windings with the 40W bulb. 7-14 and 5-10)
Line input was measured at ~122.5Vac (it was bouncing a bit.)
Winding#
7-14:
No load-125.5Vac
(40W-124.0Vac)
60W-123.3Vac
100W-121.8Vac.
5-10:
No Load 125.5Vac
(40W-124.0Vac)
60W-123.3Vac
100W-121.7Vac.
(7-14,and 5-10 appear to be identical windings.)
8-15:
No load-153.5Vac
60W-151.0Vac
100W-149.6Vac.
6-11
No load-217Vac
60W-209Vac
100W-203Vac.
20-21
No load-199.5Vac
60W-191Vac
100W-186.2Vac.
Windings 8-15,7-14,and 5-10 appear to have the highest current capability (lower DCR,and lower voltage drop with load.) Which is in-line with the testing done by Dave Paulson.
All of the heater windings were right at at 7.10Vac with no load.
(dropped a bit with the lightbulbs connected,of course.)
Just a few more tidbits of info to add to the pile.
I should have got current measurements too,doh!
I may do some more extensive testing sometime.
I grabbed a few lightbulbs,and used them as loads. a 40W a 60W and a 100W,all were 120V bulbs,made by "GE".
(I only tested 2 windings with the 40W bulb. 7-14 and 5-10)
Line input was measured at ~122.5Vac (it was bouncing a bit.)
Winding#
7-14:
No load-125.5Vac
(40W-124.0Vac)
60W-123.3Vac
100W-121.8Vac.
5-10:
No Load 125.5Vac
(40W-124.0Vac)
60W-123.3Vac
100W-121.7Vac.
(7-14,and 5-10 appear to be identical windings.)
8-15:
No load-153.5Vac
60W-151.0Vac
100W-149.6Vac.
6-11
No load-217Vac
60W-209Vac
100W-203Vac.
20-21
No load-199.5Vac
60W-191Vac
100W-186.2Vac.
Windings 8-15,7-14,and 5-10 appear to have the highest current capability (lower DCR,and lower voltage drop with load.) Which is in-line with the testing done by Dave Paulson.
All of the heater windings were right at at 7.10Vac with no load.
(dropped a bit with the lightbulbs connected,of course.)
Just a few more tidbits of info to add to the pile.
I should have got current measurements too,doh!
I may do some more extensive testing sometime.
Lastnight I did a bit more testing.
I connected each HV winding to it's own bridge rectifier,and 400V 470uf cap.Also,each cap/bridge has a 100K 'bleeder' resistor across it.
'No-Load' DC voltages: (-except for the 100K R's)
8-15 215Vdc.
7-14 175Vdc.
5-10 175Vdc.
6-11 305Vdc.
20-21 278Vdc
I connected the bridges+caps on windings 8-15 and 7-14 and 5-10 in series,and got +550V with a light 40W load (Big ~7.5K resistor)
With a LARGE 1.2K resistor,it managed 510Vdc. (at approx 425ma!) Approx 215W,by my math.
By connecting the windings in various ways you can get a wide range of B+ voltages! Approx. ~350,390,480,520,565,655V B+ are some of the combinations I came up with.
Getting 3-400ma shouldn't be much of a problem.
I've got another one of these trannies on it's way to me.
The "Monsterblocks" are in the works!
I connected each HV winding to it's own bridge rectifier,and 400V 470uf cap.Also,each cap/bridge has a 100K 'bleeder' resistor across it.
'No-Load' DC voltages: (-except for the 100K R's)
8-15 215Vdc.
7-14 175Vdc.
5-10 175Vdc.
6-11 305Vdc.
20-21 278Vdc
I connected the bridges+caps on windings 8-15 and 7-14 and 5-10 in series,and got +550V with a light 40W load (Big ~7.5K resistor)
With a LARGE 1.2K resistor,it managed 510Vdc. (at approx 425ma!) Approx 215W,by my math.
By connecting the windings in various ways you can get a wide range of B+ voltages! Approx. ~350,390,480,520,565,655V B+ are some of the combinations I came up with.
Getting 3-400ma shouldn't be much of a problem.
I've got another one of these trannies on it's way to me.
The "Monsterblocks" are in the works!
Hi everyone,
I was looking for info on Tektronix scope transformers and found this thread... I have a question that maybe somebody here can answer:
I have a 120-120 transformer. In order to tweak the HV that I want, I was thinking of incorporating some of the 6.4 volt filament windings in series with the other HV windings... Does anybody know how good the isolation is between all the 6.4 volt windings? I know one of the 6.4 volt windings has great isolation, but what about the others?
All replies appreciated.
Thanks in advance,
Daniel
I was looking for info on Tektronix scope transformers and found this thread... I have a question that maybe somebody here can answer:
I have a 120-120 transformer. In order to tweak the HV that I want, I was thinking of incorporating some of the 6.4 volt filament windings in series with the other HV windings... Does anybody know how good the isolation is between all the 6.4 volt windings? I know one of the 6.4 volt windings has great isolation, but what about the others?
All replies appreciated.
Thanks in advance,
Daniel
Last edited:
If you look at the 535/545 manual here: http://bama.edebris.com/manuals/tek/ you'll see that several windings are elevated to 100, 200, 350V (as well as the CRT winding at -1300V). So at least some are insulated to that degree. If you put those windings in series with a 120V winding with a bridge on its output (- grounded), they will never be more than 200V away from ground. Use multiple bridge rectifiers as Tek did and stack the DC supplies. No need for high voltage caps, no worries about PIV of rectifiers.
I've spent many years in the surplus test equipment business repairing those old Tek products. Those vintage scopes had power transformers that carried a virtual life time warranty. Meaning if a PT every failed, Tek would replace it and/or send you a new transformer. Of course that no longer applies anymore to the old instruments. It also doesn't apply to the newer stuff which simply isn't built as well as the old tube boat anchors. Like many companies who's products have evolved downwards, they rely on their legacy to fill some gaps. But I think you can safely assume that the transformers were made extremely well and will serve safely with what you're considering.
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