 Greetings test equipment friends. So recently I got from eBay this HP timing generator. This is model number 59308A and it came with this attached piece which is a test tone generator model 10831A. And the people who sold me this on eBay said that it does not power up so I thought it would be interesting to try to diagnose and fix this. So the purpose of at least the timing generator part of it, from what I can tell from the manual, is that it's either a digital delay generator or a precision time marker generator. So in the timer mode it basically you trigger it and then it provides a pulse a certain period after that. And you can see here that it says time in microseconds. I guess you can't go yeah you can't go lower than that so this would go only down to one microsecond. And in the time marker generator basically when you trigger it it sends out a pulse every so often according to the setting on the front panel. So there's the function switch either pacer which is the timer pulse generator or timer which is just the delay. Here's a button for triggering and resetting. In the back we can see that these are the outputs. So we have this is the trigger input and it can be triggered either positive going edge or negative going edge with a threshold set to 1 volt or 4 volts. Here's the output. The output can either be a 50 nanosecond pulse or it can be a square wave and the pulse I guess could be positive going or negative going and they've got both ECL and TTL outputs. You've got your usual HPIB setup with the address over here and here is the power input and there is the fuse. The fuse looks okay to me so why don't we just power this up and see what happens. Okay now I've plugged it in and apparently nothing is happening but then again I don't see actually a power switch on this thing. There is a power switch on this part doesn't seem to do anything but then again it has its own separate power inlet. So again this doesn't seem to do anything the on button doesn't seem to to the on LED at least or light doesn't seem to do anything and in the back I really don't see any on-off switch I mean there's there's this thing that says bus pacer. There's an internal frequency standard so we can certainly try to resolve this and the first thing that we're going to do is check that the power supply is supplying the voltages that it should. Now unfortunately it seems as though whoever scanned this manual in neglected to unfold the sheets or maybe they did fold the sheets but their software was dumb and did not recognize the width of the sheet. So this is about all we're going to be able to see of the power supply which is okay so obviously we see the inlet over here along with some filter capacitors and then we have the 115 to 230 volt selector switch then we've got a big transformer followed by on the one side we have a diode bridge along with a filter capacitor for the input what appears to be a three terminal voltage regulator and a capacitor on the output and the orientation of the capacitor tells me that this is going to be a negative voltage output that is followed by apparently another linear regulator and another connected filter capacitor on the output which again will give us some negative voltage now on the other side we can see that we have a center tapped section with a halfway of bridge the center tap goes down to ground we've got an input filter cap another linear regulator and an output with some sort of jumper and a bunch of capacitors on the outside coming from the unregulated output we have what appear to be some zener diodes we've got a 4.22 volt zener diode and then a 2.87 volt zener diode which gives us about seven volts or so so we can test this to see if it's seven volts we can test each of these linear regulators because they are probably they're probably well-known chips u 53 54 and 55 okay u 53 says it's an LM 320 h-12 regulator that would be 12 volts u 54 just says linear regulator but over here it shows that it's a 7805 which is a 5 volt regulator and then u 55 is an LM 320 5.2 volt regulator so this will be able to tell us what voltages we expect so here we are looking at the inside we can see that there is the input transformer we have some big filter caps down here let's see we've got a lot of logic chips this over here says 1826-0122 which according to the parts list is a 7805 so there's the 5 volt regulator right there we can actually probe that to see if there is 5 volts coming out alright so here we go kind of very carefully with hopefully not touching anything probe okay so I'm going to have this backwards really okay so we're getting negative or actually positive 9.9 volts on the input and on the output we're getting the expected whoops we're getting the expected 5 volts what I'm going to do is I'm going to just check some of these TTL looking chips to see if we're getting actually that power routed and yes indeed I'm getting 4.9 volts which is enough to run the logic so clearly the logic section seems to be working okay so I believe that I've located one of the voltage regulators so if let's hope that this shows up okay that's the input it's about 16 volts and the output and I've got my lead switched around so it's going to look negative so that's the output oh it doesn't look negative so that's the output it's 12 volts there's another set of three terminals over here which I think is the other voltage regulator which is a 5.2 volt regulator so if I probe that I should get something so there's 12 volts and on the other end I'm getting negative 5.2 or you know if I had my probes around the right way 5.2 volts so I know that all the voltages are being output properly so we've got 5 volts we've got 12 we've got negative 12 volts and we've got negative 5.2 volts so that then leaves the question why isn't this light turning on maybe just the light is bad so let's take that apart so this is how the front comes off and you can see that I've removed this second unit it was basically held on in the back and then there were these little grippy grippy things that hooked in to each other on the front and then basically I didn't actually have to remove that because there is nothing over here holding it on but there are screws on the top and the bottom and this just I was able to push this out because there are just these three connectors this board over here connects to these little rotary switch guys and it just comes off like that so the only thing that's left is this and we can actually see that things are labeled function so that would be this trigger reset that would be this button local PB that tells us whether the HPIB bus is controlling the device or if we're controlling it locally and then there's addressed remote and on on is the thing that I'm interested in so the other thing that we could do is we could just hook up power supply up to it and a resistor and see if we can get these things to light up that's probably the easiest thing to do just to make sure that this that this LED actually does work if it is indeed an LED now that I look at it it kind of sort of looks like there are lamps and unfortunately the schematic doesn't say anything if there are lamps then they would have a resistance so let's see if there's a resistance showing up no I don't see it well okay I don't see any resistance across this thing which could mean that it's burned out let's try on this side we're getting a resistance of 11 ohms across that one and 12 ohms across this one so in fact the only thing wrong with this piece of equipment is that there is a bulb here that is burned out so I would just have to find out what the voltage and resistance rating or current rating of this bulb is and just replace it so what I'm going to do is I'm just going to desoldered that and take a look at it to see what I can find okay so I just quickly desoldered this bulb so let's see what we have to see does this actually come out doesn't seem like it does this may in fact be all one piece which is not great because that's pretty custom looking so let's see what sort of voltage we're getting across that bulb huh five volts so that's actually interesting that's five volts DC is there any AC voltage on that no it doesn't look like there's any AC voltage so this is basically a simple five volt TTL output and we can just slap an LED across it with a resistor yeah that's that's actually getting a little more dim let's where is the front panel maybe I should see what it looks like through the front panel so may not be the best LED for it but actually that doesn't really look too bad how about we stick with that sure all right let's see how it looks it lights up it looks pretty good to me I did look on Mouser and Digikey to see if I could find this bulb the parts list says that this is a T1 and three-quarters bulb that refers to the lens size and it's five volts there was even a manufacturer and a manufacturer number the manufacturer no longer exists and a Google search for the part number turns up absolutely nothing I didn't find anything that looked anything like this I did find bulbs that went up to maybe about here and then had a bulb on top that might have actually worked but I also looked at the specification of this sort of bulb and they draw something like a hundred milliamps which is quite a lot whereas this draws barely a fraction of a milliamp now I don't know if you can see this this sort of bright spot that's not a camera effect or a lighting effect there was actually a label sitting on top of here and when I removed it you could see a very definite color difference between what was under the label and the rest of the thing it looks like I don't know this has been sitting around for well I mean if the chips are from 1983 it's been pretty much 35 years so that's 35 years of ultraviolet I might try the retro brighting technique on this this is just plastic it's not metal again this is extremely cheaply made there are these labels in here which I don't think will work very well for the retro brighting process but that's on the bottom this is on the top and the top is definitely a browner than the bottom so I also took the labels off of here and that worked pretty well so and in case you're wondering I did actually test that the square wave function worked it turns out that there was a little note here that says output not square when exponent equals 0 and I did have the exponent here set to 0 so instead I just set it to 5 times 10 to the 1 or 50 microseconds and it was bang on 50 microseconds so I changed this and the frequency definitely did change and it was a nice square wave so anyway there we go that's about it thank you very much bye