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pma

pma

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Pinouts on the TO-92s...
Oh no. But the VAS transistor physical placement on the PCB is reversed against schematics (it was better re PCB tracks) - I was lazy and modified one of the older PCB designs to keep big tranies position because of existing drills in the heatsink. But I was not careful on parts soldering, placed parts by memory and swapped NPN and PNP VAS parts. Horribly high PSU current, but rail test setup current limiting resistors saved it and nothing went to fire and no part failure except for one of the rail test setup protective resistors. 2 x 58V rails are a lot.

You might like the 20kHz 4ohm power
20k_4R.png

same as for 1kHz. Please forgive the digital 8-bit scope.


10kHz 20Vpp square
10ksq_4R.png



I will make a set of measurements and open a thread in DIY forum section. One of the few DIY projects here ;)
 

restorer-john

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You might like the 20kHz 4ohm power

Love it. 20kHz full power test is necessary for any amplifier on my bench. Square wave looks good- that's 20Vpp into 4R too?

Nothing wrong with the 8 bit scope- you can always turn on averaging/persist to clean it up. Is that the UNI-T PC software? Sure, a CRO looks better, but I have to take a picture with a camera, whereas the Rigol has the screen capture utility and control software. I really only like the DSOs for automatic measurements, zooming in and finding runt/glitches. For everything else, I still use my old skool CRO. They sit side by side. I used to have my old Trio 60MHz on top but sent it to the storeroom. I miss it sometimes.

261W! So your rails are dropping about 10V under full load. One transformer for each channel?

If it's a rainy weekend, I'm going to finish the L-85V restoration and post up some performance figures if I finish it before Monday. I've got some noisy differential front end transistors, so I may be going through the bag and matching up on the curve tracer.
 
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pma

pma

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Love it. 20kHz full power test is necessary for any amplifier on my bench. Square wave looks good- that's 20Vpp into 4R too?

Nothing wrong with the 8 bit scope- you can always turn on averaging/persist to clean it up. Is that the UNI-T PC software? Sure, a CRO looks better, but I have to take a picture with a camera, whereas the Rigol has the screen capture utility and control software. I really only like the DSOs for automatic measurements, zooming in and finding runt/glitches. For everything else, I still use my old skool CRO. They sit side by side. I used to have my old Trio 60MHz on top but sent it to the storeroom. I miss it sometimes.

261W! So your rails are dropping about 10V under full load. One transformer for each channel?

If it's a rainy weekend, I'm going to finish the L-85V restoration and post up some performance figures if I finish it before Monday. I've got some noisy differential front end transistors, so I may be going through the bag and matching up on the curve tracer.

We are on the same wave, John.

The rails are dropping to 2 x 51V at full power. Please take into account 2xVbe additional drop for 2EF: driver + output transistor. And something on the VAS as well. One 300VA transformer per each channel = 2 transformers per stereo. So as long as the mains voltage holds, 1 channel or 2 channel power makes no difference and also the PSU drop related interchannel modulation is excluded.

Looking forward your restored L-85! However it is quite a different circuit. It has 2 input differential gain stages in series and no EF VAS buffer. @sabristol in fact created a new circuit that is very very similar to Douglas Self's Blameless amplifier and not so similar to Luxman. Only that he put it into the Luxman case.
 

restorer-john

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Only that he put it into the Luxman case.

For me, I love the perfect restoration and I only make modifications where there were flaws/faults/reliability issues etc. I have so many amplifiers that it is not the search for the perfect one, but which one to play with today. ;)

But @sabristol has done a great job on what was probably just a fun project amp for him. A long term project for sure. Most likely the original boards got hacked-up or charred-up back in the day and got separated from the amp (ask me how I know things get separated and 'lost').

I think he's done a excellent job and I really like your new design too. Have you ever done designs where you rectify the secondary twice, once for the main OPTs and drivers and a full wave and filter capacitance for the front end/VAS? Off the same main HV secondaries, not a separate higher voltage tapping. Sony called it 'spontaneous twin drive'.
 
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pma

pma

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For me, I love the perfect restoration and I only make modifications where there were flaws/faults/reliability issues etc. I have so many amplifiers that it is not the search for the perfect one, but which one to play with today. ;)

But @sabristol has done a great job on what was probably just a fun project amp for him. A long term project for sure. Most likely the original boards got hacked-up or charred-up back in the day and got separated from the amp (ask me how I know things get separated and 'lost').

I think he's done a excellent job and I really like your new design too. Have you ever done designs where you rectify the secondary twice, once for the main OPTs and drivers and a full wave and filter capacitance for the front end/VAS? Off the same main HV secondaries, not a separate higher voltage tapping. Sony called it 'spontaneous twin drive'.

Yes I did, of course that higher supplies for VAS make higher usable output power, just take care of overdriving.

The only difference between us (re electronics :D) is that you love restoration of old units and I sincerely hate it and put the thing into dust bin if it no longer works :D. On the other hand, I love circuit hints and try to tune them and build and verify, like Brabus, you know :D.

This is the 56Vpeak-peak 4ohm 19+20kHz CCIF measurement on the new amp, the test that @amirm doesn't like to use ;)
250W4Ramp_CCIF_56Vpp_4R.png


Still a lot of workbench tests ahead of me.
 

boXem

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Yes I did, of course that higher supplies for VAS make higher usable output power, just take care of overdriving.

The only difference between us (re electronics :D) is that you love restoration of old units and I sincerely hate it and put the thing into dust bin if it no longer works :D. On the other hand, I love circuit hints and try to tune them and build and verify, like Brabus, you know :D.

This is the 56Vpeak-peak 4ohm 19+20kHz CCIF measurement on the new amp, the test that @amirm doesn't like to use ;)
View attachment 119077

Still a lot of workbench tests ahead of me.
That's pretty good!
 

Rick Sykora

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Our Canon MF229dw...

A461D806-0EF2-45E9-A582-B9654D5E7526.jpeg

is the workhorse printer in our office. When my wife said it exploded a couple of weeks ago, was sure it was a cap gone bad. It turned out to be one of these...
8D0CAC8B-8BBB-402B-8E10-3F25F14AC8B7.jpeg

That is the right ADF hinge that helps hold up the top half of the printer. As you might surmise, you should not be seeing the spring. Fortunately, the printer kept working fine. Was considering a wholesale replacement as it is a few years old, when I found the replacement hinges on ebay for $12. It was shipping standard post, but looked like I could wait. It arrived yesterday.

While this would seem to be a mechanical repair, both hinges needed to removed and the left one would not come out as it had all the wiring alongside it. Fortunately, there was a youtube video for the repair. You have to take off a side cover and detach all the cable connectors. That looks like this...

8DB4EC6D-5489-4C89-B58E-30D22774D11B.jpeg

Yes, you need to disconnect all that cabling except for the blue ones on the left. Then you can remove the left hinge! Anyway I do not do this much, so may just be easily impressed, but what you see above the ribbon cables are pairs of flat ferrites around each cable. Had not seen those on a ribbon cable before.

Anyway, the printer is buttoned back up and working fine. I otherwise may not have put in the effort, but the toner cartridges for the this printer are only around $10 each and the appraisal business prints a lot of documents. :)
 
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restorer-john

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I wanted a portable 2 channel arbitrary waveform generator with reasonable performance for quick tests. I figured this little UNI-T UTG962E at 60MHz/200MSa/S and a 14 bit vertical resolution might be OK. Was not expecting DDS sines to be low THD, but I was surprised.

Took a chance on Ali-Express and despite the seller wanting to delay my order (which I said no, just refund it and he miraculously sent it same day...) , it turned up within a few weeks and all is good.
IMG_4112 (Medium).jpeg


THD is better than I expected to be honest and quite usable for basic on the go testing. Some great arbitrary functions, linear and log sweeps etc. Waveforms can be uploaded via software/USB port which I haven't tried yet. No fan and very compact, but a huge display and logical controls.

Lots of relays on range changes and all the buttons and controls are actually very decent. Overall, very surprised how well made it is.

IMG_4114 (Medium).jpeg


IMG_4115 (Medium).jpeg


Only pulls 930mA@5V with both outputs on. 100mA less with the outputs off.
IMG_4118 (Medium).jpeg


IMG_4120 (Medium).jpeg


Rise time square at 22KHz was 13nS.
Sinc
IMG_4122 (Medium).jpeg


IMG_4123 (Medium).jpeg


Pretty decent for an inexpensive DDS. The supplied 5V@2A plugpack is not earthed. As such the 0V (and the BNC outputs) sit at 60V (floating high imp- not dangerous). This could a) account for some of the 50Hz harmonics and b) could be fun and games into the front end of sensitive gear. I'm going to try my properly earthed bench supply on 5V and compare.

But overall, it's an amazing little thing.
uni-t utg962e.png


Some pics of the guts on EEV blog
https://www.eevblog.com/forum/testg...function-arbitrary-waveform-generator-220394/
 
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OP
pma

pma

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I wanted a portable 2 channel arbitrary waveform generator with reasonable performance for quick tests. I figured this little UNI-T962E at 60MHz/200MSa/S and a 14 bit vertical resolution might be OK. Was not expecting DDS sines to be low THD, but I was surprised.

Good. It is not usable for audio distortion testing, but perfect for design and repair phase, step responses, slew rate measurements etc.

I was using a similar generator to test above "audio band", see below (yes it is an audio preamp)

D2_.JPG


I have then built my own function generator based on MAX038 that goes up to 30MHz

gen001.JPG
 

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restorer-john

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The little UNI-T generator software works perfectly too. Full PC control of the unit via USB including creating and uploading arbritary waveforms etc.

Here's the virtual control
control.png

And a screen grab
gen screenshot.png


Most impressive for so little money.
 

egellings

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A little ol' Dynaco ST-35 power amp with 6BQ5 peanut pentodes. I'm trying the Dave Gillespie EFB mod on it.
 
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