No gentle reader, you are not experiencing deja vu, nor is this a leg pull. It has made me wonder about fanciful ideas such as morphic resonance and synchronicity.
These two Hitachi V-422 scopes came from the same swapmeet as the two Hamegs, but from a different seller. One I was told showed some signs of life, the other was dead. After a brief negotiation I came away with the pair for less than the two Hamegs, this time the price of a packet of 20 cheap gaspers.
Both were covered in grime and stickers, worse than the Hamegs, but both were complete, with no missing knobs and nothing worse than a few chips in the plastic fittings. They have consecutive serial numbers. I'd guess they were bought by a company around 1990, used for years, then thrown in a junk room when they started to act up, and appeared at the swapmeet when they were eventually cleared out.
Hitachi V422 (shows signs of life)
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Had a sticker saying "For reference only. Not to be used for measurement". I powered it up and it produced traces on some attenuator settings and some timebase settings. Removed the cover and front fascia and gave them a thorough clean and removed stickers. Removed internal dust with a paintbrush and vacuum cleaner. Cleaned all switches with IPA. Removed the XY board and cleaned the attenuator switches. I learned on the WWW that they can be pried open a little and DeOxit squirted in, which avoids a lot of risky dismantling.
Freed shafts with stiffened grease and relubricated. Put it back together. Powered it up and checked voltages and ripple - no problems. Went through the set up procedure in the manual a couple of times. Left it running overnight. Everything checked out the next day. Left it powered down for a day and checked it out again. No problems. All a bit boring. I didn't even change the main caps in the PSU.
Hitachi V422 (dead)
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Had a sticker saying "No Power. Do not use". I checked the mains fuse, the power switch and the mains transformer windings for continuity. Looked and sniffed for anything burned or damaged. Nothing obvious. Powered it up and the power light did not come on. It's powered by the 8V supply. Power was going into the PSU circuitry from the transformer, but there was no voltage in the PSU. Took out the board and checked for continuity - dry joints on the header bringing in power, confirmed with a magnifying glass. Remade the joints. Checked the board and found a burned out resistor across the input and output of a three terminal regulator. I've see diodes used there to stop the regulator being wrecked by back current, but never a resistor. Replaced the 1/8th Watt (at least very small) resistor with a 0.6 Watt metal film type. Powered up the board using a bench power supply to current limit it and check current, and avoid the trouble of replacing it only to find something else wrong. It seemed OK.
Everything was cleaned and put right as with the first scope.
Went through the set up procedure, but couldn't get the gain on Channel I right. The display went all over the place when I pushed the preset with the adjusting tool. I happened to have a 200R cermet preset of the same pattern in the collection, so out came the board and the preset was changed.
Everything seemed OK now, apart from the Add Balance, which I noticed couldn't be adjusted properly. This caused some head scratching and investigating with a DMM and another scope.
It turned out to be caused by a the set up being very twitchy. I thought it might be something like a dry joint, but when it was got right, no amount of prodding the resistors likely to affect it, with an adjustment tool, altered it. I'm sure I didn't have the problem with the other one. Left it running overnight as with the other one. All functions work properly, no problems I can find.
Anyway, two pleasant to use analogue 40MHz scopes. The 3dB point is comfortably over 40MHz. They have very sharp displays. I prefer using them to the Hamegs. The manuals are better and they are easier to work on. I don't like the tiny little resistors they used. Most of the knobs have splines rather than grub screws. Sometimes they take what seems like unreasonable force to remove and they can be very hard to re-fit.
A Tale of Two Hitachi 40MHz scopes
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A Tale of Two Hitachi 40MHz scopes
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Re: A Tale of Two Hitachi 40MHz scopes
Yup. There's a reason my fugly little V-212 lingers. It's cockroach TE; boringly dependable.
mnem
click.
mnem
click.