Yup it was a 225... SSTOR was my friend many times as was debug g=c800:5
When they were not reading anymore but still seeking, we'd take off the cover and watch it while running "coretest"... It sucked as a benchmark so bad we hex edited the EXE so it would display "Blowtest"... EDIT: I found BLOWTEST.EXE in my dos archive but I can't attach an EXE file...
Disk Utility: Coretest V.2.92 : Free Download, Borrow, and Streaming : Internet Archive
The ones with the green board worked better than the ones with the gold board...
I once recovered a 40MB Quantum IDE drive by shaking the entire computer it was mounted in the same way it spins to overcome "sticktion"... After that, the teacher just left it running 24/7...
Imagine the capacity of a HH 5 1/4" HDD today?! Like 100 TB or something.
When they were not reading anymore but still seeking, we'd take off the cover and watch it while running "coretest"... It sucked as a benchmark so bad we hex edited the EXE so it would display "Blowtest"... EDIT: I found BLOWTEST.EXE in my dos archive but I can't attach an EXE file...
Disk Utility: Coretest V.2.92 : Free Download, Borrow, and Streaming : Internet Archive
The ones with the green board worked better than the ones with the gold board...
I once recovered a 40MB Quantum IDE drive by shaking the entire computer it was mounted in the same way it spins to overcome "sticktion"... After that, the teacher just left it running 24/7...
Imagine the capacity of a HH 5 1/4" HDD today?! Like 100 TB or something.
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Look at price VS capacity.
Those 20 MEGAbyte Seagates cost $200 to $250 in the 80's. That's like what, $500+ today for 0.0002TB today.
I remember forking over $450 each for two ST4096 80 MB drives. They were full height 5 1/4 inch drives that weighed in at about 4 pounds and had 5 or 6 platters (don't remember which). I had two of them in my MegaMachine that ran a 16 MHz 80386 at 40 MHz. I had to put a switch on the 12 volt lead to one of them because the power supply couldn't spin both of them up at the same time.
I guess things have changed a little......
Those 20 MEGAbyte Seagates cost $200 to $250 in the 80's. That's like what, $500+ today for 0.0002TB today.
I remember forking over $450 each for two ST4096 80 MB drives. They were full height 5 1/4 inch drives that weighed in at about 4 pounds and had 5 or 6 platters (don't remember which). I had two of them in my MegaMachine that ran a 16 MHz 80386 at 40 MHz. I had to put a switch on the 12 volt lead to one of them because the power supply couldn't spin both of them up at the same time.
I guess things have changed a little......
Yup. I'm young enough to have paid 1$ /MB for them used as a kid...My first machine at home was a Xerox "820-II" with the 8 inch floppies... My first "real" computer was an Olivetti 8086 @ 8 MHz. It ran DOS* and it was the first example of x86 I used. With DOS 2.11!
My life 25 odd years ago and I assure you, this wasn't nearly as "fast" or "smooth" on a 486. Even with good hardware. Indeed, the "waves" near the end of this we refered to as "the P5 segment" as in you needed a Pentium...
Second Reality by Future Crew/url]
My life 25 odd years ago and I assure you, this wasn't nearly as "fast" or "smooth" on a 486. Even with good hardware. Indeed, the "waves" near the end of this we refered to as "the P5 segment" as in you needed a Pentium...
Second Reality by Future Crew/url]
This Wharfedale SPC-12 piece of garbage SMPS, for the second time [emoji28] different fault, at least ¯\_(ツ)_/¯
https://www.diyaudio.com/forums/showthread.php?p=6124147
https://www.diyaudio.com/forums/showthread.php?p=6124147
Found s strange thing in a USB scope I designed.
On the print out the waveform touched top and bottom on screen but not printout.
Turned out i was using screen height as a parameter instead of printer page height.
To try and be clever the scope screen is displayed as 60% of screen height which means all measurements for graticule, waveform etc have to be scaled to 60% of screen height.
Good fun....
On the print out the waveform touched top and bottom on screen but not printout.
Turned out i was using screen height as a parameter instead of printer page height.
To try and be clever the scope screen is displayed as 60% of screen height which means all measurements for graticule, waveform etc have to be scaled to 60% of screen height.
Good fun....
Fixed a 36V SMPS.
I changed to four electros and all is good.
AC-DC 100-240V to 36V 5A 180W 50/60HZ Power Supply Switching Board Module dQQ9 | eBay
I changed to four electros and all is good.
AC-DC 100-240V to 36V 5A 180W 50/60HZ Power Supply Switching Board Module dQQ9 | eBay
I can't even tell you how many capacitors I've changed in VCR SMPS over the decades.
As much as I loathe SMPS, it kept me and the shop busy for 25+ years.
And.....
I got a sweet VCR in the deal too....
A woman brought in a 1986 GE VCR, apparently dead.
Her son bought it for her as a Christmas gift.
This GE model was made by Panasonic, and had to be their top of the line machine. (MSRP $890.)
Digital freeze frame, picture-in-picture, cast aluminum mechanism, all sorts of editing features and 42 controls, soft drop-down access door, LED level/tracking meters, illuminated cassette chamber, the works.
All it needed was some SMPS repairs - I quoted $80.
The woman nicely told me to keep it, she'd go to Walmart and buy another machine - she only used it for the clock anyway.
This machine never even saw a tape loaded into it!
What you can't see in the photo is the plethora of touch pad controls in the drop down door.
I still have it, and it runs like a champ.
Attachments
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I must have 60 or so Laserdiscs too -- found one LD player in the Millburn NJ Town Dump.
For a brief period of time in the latter 1980s/early 1990s, some VCRs were the best consumer device for recording Hi-Fi stereo audio.
Super VHS + Hi Fi, I think it was called; the audio was laid down in stripes across the tape by the rotating heads, just like the video. This extended audio bandwidth from below 20 Hz to above 20 kHz. Other audio specs were remarkably good for the time too, far better than audio cassettes ever were, for instance.
A small, innovative American audio company took that idea and ran with it, managing to cram 8 tracks of CD-quality digital audio onto S-VHS tapes instead of the video signal. The Alesis ADAT cost $4000, at a time when the only competition - conventional analogue studio 8-track reel-to-reel machines with wide tape formats - cost ten to twenty times as much, not to mention the low cost of blank S-VHS tapes compared to the cost of pro reel-to-reel tape.
Sadly, Alesis didn't wake up to the reality of hard-disc recording and leaned on their flagship product far too long. Combined with the dot-com collapse of the late 1990s and various other poor management decisions, the company went bankrupt, and assets were sold for pennies on the dollar. The name "Alesis" was purchased by another larger audio corporation, but only the name remains; the creative engineering of the original company is gone for good.
-Gnobuddy
Hi Gnobuddy,
The Alesis ADAT was a VCR transport and suffered greatly from being that cheap format. They went out of alignment extremely easily even right after being aligned. I looked at that product as a warranty contract, and that tendency removed it from consideration.
It was a neat idea, but you can't use a cheap mechanism and cheap tape format and expect to get great performance out of it reliably. I know some were not that bad, but the average was. Instead we went with the Tascam format that went on to dominate that market segment. Even video post production used the Tascam format for audio. The cost of the Tascam system wasn't even twice as much, and it was very reliable.
The Studer 8 track machines had better performance than the A-DAT did, and was the definition of reliability. Comparing an A-DAT to a Studer can't be done without clearly stating the differences. Then the price differential makes sense.
-Chris
The Alesis ADAT was a VCR transport and suffered greatly from being that cheap format. They went out of alignment extremely easily even right after being aligned. I looked at that product as a warranty contract, and that tendency removed it from consideration.
It was a neat idea, but you can't use a cheap mechanism and cheap tape format and expect to get great performance out of it reliably. I know some were not that bad, but the average was. Instead we went with the Tascam format that went on to dominate that market segment. Even video post production used the Tascam format for audio. The cost of the Tascam system wasn't even twice as much, and it was very reliable.
The Studer 8 track machines had better performance than the A-DAT did, and was the definition of reliability. Comparing an A-DAT to a Studer can't be done without clearly stating the differences. Then the price differential makes sense.
-Chris
My garage amp.
The output transistors died due to loose aluminium shavings behind the pcb.
I didn't have any Mjl3281/1302 left, so I installed some sankens instead.
Warming it up and adjusting bias before I put the amp back together and carry it out in my garage.
The output transistors died due to loose aluminium shavings behind the pcb.
I didn't have any Mjl3281/1302 left, so I installed some sankens instead.
Warming it up and adjusting bias before I put the amp back together and carry it out in my garage.
Attachments
Bro has started using his stereo again.
Marantz CD46 - 'no disc' error & horrendous (fingernails on blackboard) drawer noise.
Drop of lube on belt pulley spindles silenced it & it now reads discs.
Rotel ra-920ax blown diode bridge & internal fuses.
Replaced with one from a dead ATX power supply, new fuses & now works.
Might let it bed in then recheck bias & DC offset. Could be a while though due to reduced socializing.
My sort of repairs - simple & obvious.
Marantz CD46 - 'no disc' error & horrendous (fingernails on blackboard) drawer noise.
Drop of lube on belt pulley spindles silenced it & it now reads discs.
Rotel ra-920ax blown diode bridge & internal fuses.
Replaced with one from a dead ATX power supply, new fuses & now works.
Might let it bed in then recheck bias & DC offset. Could be a while though due to reduced socializing.
My sort of repairs - simple & obvious.
Last repair; a couple of years ago, on the week of my retirement.
I looked on the shelf and there was a shiny (and fearsome looking) Yamaha MCX-1000, along with a replacement optical drive waiting to be fitted.
I picked it up and looked at the jobsheet. The tech that had started this unit had ordered a new optical drive along with a copy of the installation software, since this is needed to install a new drive. This was actually the third replacement drive received, the first two (and this one) being received with transit damage.
I opened one of the damaged drives, to find the base of the mechanism was cracked, so I set to work transplanting the laser assembly from a damaged unit to the Yamaha’s own drive, which could not read a disk.
The unit fired up fine and, since I had not replaced the drive electronics, the installation software was not required.
A quick test and the unit appeared to be working, but when I listened to the playback, it was horrendously distorted, as was playback of the customers HDD recorded material.
Looking at the playback waveform, it was being “sliced up” at mains frequency. After 20 minutes checking around then playback PCB, I discovered that PMUTE was the culprit.
Clearly, this unit was designed by someone who has never actually serviced a product. You put the bits which are never likely to fail at the bottom, and things like the power supply at the top.
To get to the power supply required the whole unit to be dismantled, took around two hours. When I finally got to the power supply, R419, C433, C439, C441 and a few other components were open circuit.
After replacing these and rebuilding the unit, it gave a superb account of itself; but I am truly glad I will never meet one of these again.
I looked on the shelf and there was a shiny (and fearsome looking) Yamaha MCX-1000, along with a replacement optical drive waiting to be fitted.
I picked it up and looked at the jobsheet. The tech that had started this unit had ordered a new optical drive along with a copy of the installation software, since this is needed to install a new drive. This was actually the third replacement drive received, the first two (and this one) being received with transit damage.
I opened one of the damaged drives, to find the base of the mechanism was cracked, so I set to work transplanting the laser assembly from a damaged unit to the Yamaha’s own drive, which could not read a disk.
The unit fired up fine and, since I had not replaced the drive electronics, the installation software was not required.
A quick test and the unit appeared to be working, but when I listened to the playback, it was horrendously distorted, as was playback of the customers HDD recorded material.
Looking at the playback waveform, it was being “sliced up” at mains frequency. After 20 minutes checking around then playback PCB, I discovered that PMUTE was the culprit.
Clearly, this unit was designed by someone who has never actually serviced a product. You put the bits which are never likely to fail at the bottom, and things like the power supply at the top.
To get to the power supply required the whole unit to be dismantled, took around two hours. When I finally got to the power supply, R419, C433, C439, C441 and a few other components were open circuit.
After replacing these and rebuilding the unit, it gave a superb account of itself; but I am truly glad I will never meet one of these again.
I was testing a new amp build.
Its a fairly basic classic class AB amp with ltp, VAS into irfp240/9240 outputs.
I made the LTP from a pair of depletion mosfets.
I wanted to make sure it worked rail to rail so wound up my sig gen.
The dc protection box I have clicked out and so something must have gone wrong and put DC on the output. I had 45 volts on the output when I checked.
I found the depletion mosfets had blown so replaced them.
I had a quick look at sig gen output and it was greater than 20 volts ac so had blown the depletion mosfets.
I tested it again being a bit more careful with the sig gen and it worked fine.
Its a fairly basic classic class AB amp with ltp, VAS into irfp240/9240 outputs.
I made the LTP from a pair of depletion mosfets.
I wanted to make sure it worked rail to rail so wound up my sig gen.
The dc protection box I have clicked out and so something must have gone wrong and put DC on the output. I had 45 volts on the output when I checked.
I found the depletion mosfets had blown so replaced them.
I had a quick look at sig gen output and it was greater than 20 volts ac so had blown the depletion mosfets.
I tested it again being a bit more careful with the sig gen and it worked fine.
