Hi djn,
Now there's how to begin a tough repair.
Hi Rick,
I use a scope when aligning a tuner some times. For one, it allows you to see the level of an RF envelope as you tune the front end if the set uses LEDs for signal strength. For troubleshooting, a scope is pretty handy to have and can really save your bacon. I even have to use a spectrum analyzer some times. Keep in mind that I tend to get failed repairs and alignments. You never know what a panicking technician will do.
When my Philips scopes are idling as I do an alignment, they interfere with the tuner. This is with no connection to the equipment, not even a ground clip. Additionally, when you set the VCO free run for the MPX (if used), I check the waveform so I know what it is that I'm measuring. Two scopes even have built in frequency counters (My Agilent is hands free, the Tek needs to have cursors adjusted). At any rate, it's too bad because those Philips scopes are quite nice.
-Chris
Now there's how to begin a tough repair.
Hi Rick,
I use a scope when aligning a tuner some times. For one, it allows you to see the level of an RF envelope as you tune the front end if the set uses LEDs for signal strength. For troubleshooting, a scope is pretty handy to have and can really save your bacon. I even have to use a spectrum analyzer some times. Keep in mind that I tend to get failed repairs and alignments. You never know what a panicking technician will do.
When my Philips scopes are idling as I do an alignment, they interfere with the tuner. This is with no connection to the equipment, not even a ground clip. Additionally, when you set the VCO free run for the MPX (if used), I check the waveform so I know what it is that I'm measuring. Two scopes even have built in frequency counters (My Agilent is hands free, the Tek needs to have cursors adjusted). At any rate, it's too bad because those Philips scopes are quite nice.
-Chris
I fixed up a fella's Sencore SG165 -- had some issues with the FM oscillator. Turned out that the issue related to someone elses attempt to align the "bandspread". This just takes a bit of patience.
I’ve got a windows PC. First windows box I’ve had in ten years (I use macs, and have been running windows in a virtual machine when needed).
It started with scoring some free GPIB cables. I used them to connect my HP 3585B, 2235B, 3478A, and Tek TDS340A together. Then I got on line and bought a cheap NI GPIB-USB-A converter, which I plugged into my mac. I couldn’t find mac drivers and couldn’t get it to work under the virtual machine (a problem I’ve been battling for years with my EPROM programmer).
So I went back online and bought a cheap PC for $50. I didn’t want to waste any more bench space than I had to, so got a HP DC7900 USDT box, which is quite demure. It came with windows 7. I found it was tragically slow to boot, so bought an SSD for it (another $50) and 4GB of RAM (another $50). I used my mac to clone the hard drive onto the SSD, and while that was doing it’s thing I repainted the top and bottom covers, which were badly scratched, with some engine enamel that I had left over from work on my motorbike.
The extra couple of things on the bench that need mains power also forced me to clean up the whole power issue. I mounted three powerboards to the underside of the bench. One 4-outlet one with RCD, which feeds a couple of 8-outlet ones, so I’ve got 18 outlets in total, all protected by a local RCD in addition to the one in the switchboard. Big loads (like amplifiers under test) go straight to the 4-outlet one, and all the myriad tens-of-watts loads fo to the 8-outlet ones.
Anyway, I reckon it’s come up quite nicely, not a bad weekend’s work. The only remaining thing is to replace the fans in the PC (funnily enough, another $50), as the ones in it are on the annoying side.
It started with scoring some free GPIB cables. I used them to connect my HP 3585B, 2235B, 3478A, and Tek TDS340A together. Then I got on line and bought a cheap NI GPIB-USB-A converter, which I plugged into my mac. I couldn’t find mac drivers and couldn’t get it to work under the virtual machine (a problem I’ve been battling for years with my EPROM programmer).
So I went back online and bought a cheap PC for $50. I didn’t want to waste any more bench space than I had to, so got a HP DC7900 USDT box, which is quite demure. It came with windows 7. I found it was tragically slow to boot, so bought an SSD for it (another $50) and 4GB of RAM (another $50). I used my mac to clone the hard drive onto the SSD, and while that was doing it’s thing I repainted the top and bottom covers, which were badly scratched, with some engine enamel that I had left over from work on my motorbike.
The extra couple of things on the bench that need mains power also forced me to clean up the whole power issue. I mounted three powerboards to the underside of the bench. One 4-outlet one with RCD, which feeds a couple of 8-outlet ones, so I’ve got 18 outlets in total, all protected by a local RCD in addition to the one in the switchboard. Big loads (like amplifiers under test) go straight to the 4-outlet one, and all the myriad tens-of-watts loads fo to the 8-outlet ones.
Anyway, I reckon it’s come up quite nicely, not a bad weekend’s work. The only remaining thing is to replace the fans in the PC (funnily enough, another $50), as the ones in it are on the annoying side.
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Looking very good Suzy!
You don't want to see the AC power bars I have under my bench. 3 x 12 socket power bars and I just bought another to add to it. I'm running out of outlets! I have them screwed to the cross bar. It will fit 4 total. I have another 6 outlet unit on top of the bench as I didn't want more cords cascading down from the top of the bench.
I think I'm going to run another circuit to the bench for the unit under test as some amplifiers are pretty power hungry these days.
-Chris
You don't want to see the AC power bars I have under my bench. 3 x 12 socket power bars and I just bought another to add to it. I'm running out of outlets! I have them screwed to the cross bar. It will fit 4 total. I have another 6 outlet unit on top of the bench as I didn't want more cords cascading down from the top of the bench.
I think I'm going to run another circuit to the bench for the unit under test as some amplifiers are pretty power hungry these days.
-Chris
When I worked, my shop was cited by the fire inspector. I ended up with three 20A circuits and eight 10-outlet boxes, over 80% full.
Here at the PC I am ashamed to report that my one 10-way box (followed me here) is only half full, though there is a 4-way hung on that, and the garage is a whole 'nother story.
...and the unit specifically cant be used with metal tapes only Type 1..A KLH model Eighteen FM tuner and a yet uncompleted homebrew voltage & current metered "variac" which uses the Superior Electric Powerstat flavor of adjustable autotransformer. This one is rated for 12 Amps continuous current.
From the tuner's audible symptoms I am pretty sure it's the electrolytics in its power supply at blame. I'll know sometime today once I replace the two 500 uF cheesebag looking PSU filter caps.
From the tuner's audible symptoms I am pretty sure it's the electrolytics in its power supply at blame. I'll know sometime today once I replace the two 500 uF cheesebag looking PSU filter caps.
I’ve been searching ebay for HP stuff, on account of recently getting a little HP DC7900 small form factor windows XP PC for talking to instruments.
An old HP85 came up locally, with a dead display. I thought why not, and put a lowball bud on it, and got it.
On the bench, there’s video there, and it’s obviously scanning, but it’s just really badly smeared and unreadable. Before spending more money on a CRT for it, I ran the cro over the video signals, and found the video line at the tube was pulling low, but not pulling back high.
I downloaded the service manual for it, and noted the video output to the tube has a PNP transistor pulling high. I could see stuff happening at the base, but nothing on the collector. Alas no clue in the manual what it is, and it’s got a HP part number. I pulled it and couldn’t measure Vbe, so figured I’d try replacing it. I chose a 2SA1381 on account of having ample voltage and current capability to drive the output, and being reasonably fast so good for video.
And up it came
It’s not over yet. I have to fix the tape drive yet (decomposed capstan), and get a HP-IB module for it before it becomes useful.
I miss the days when you could buy a computer, turn it on, and write code to do things.
An old HP85 came up locally, with a dead display. I thought why not, and put a lowball bud on it, and got it.
On the bench, there’s video there, and it’s obviously scanning, but it’s just really badly smeared and unreadable. Before spending more money on a CRT for it, I ran the cro over the video signals, and found the video line at the tube was pulling low, but not pulling back high.
I downloaded the service manual for it, and noted the video output to the tube has a PNP transistor pulling high. I could see stuff happening at the base, but nothing on the collector. Alas no clue in the manual what it is, and it’s got a HP part number. I pulled it and couldn’t measure Vbe, so figured I’d try replacing it. I chose a 2SA1381 on account of having ample voltage and current capability to drive the output, and being reasonably fast so good for video.
And up it came
It’s not over yet. I have to fix the tape drive yet (decomposed capstan), and get a HP-IB module for it before it becomes useful.
I miss the days when you could buy a computer, turn it on, and write code to do things.
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That brings back memories, I remember running HPL on them. Nice that you could get a service manual and get it going some what. When I worked at Motorola, they used them for many purposes, to run test stations. What was the networking? HP version of token ring iirc? this was before 10M ethernet.
Other than sending out control and receiving measurement data, not sure how you are to log this information if you need access to it.
Other than sending out control and receiving measurement data, not sure how you are to log this information if you need access to it.
They had HP85's for sale in the McGraw Hill bookstore on 6th Avenue -- back around 1979-80. (MH bookstore had an enormous selection of books on engineering, the sciences, economics etc.)
Yes, I will. I can get a cheap GPIB interface for it, and there’s a project online for building a HPIB SD card disk drive, which works with the 85B. "GPIB Disk emulator"
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