- Use of non-screened transformer in old monitor - 1 Update
- HITACHI V-353F OSCILLOSCOPE V-353-F - 8 Updates
| Jon <jms019@gmail.com>: Mar 18 09:42AM -0700 It is now fine with a toroidal transformer. It looks like the electrostatic screening of the original was less important than the magnetic screening. Jon |
| jurb6006@gmail.com: Mar 17 08:29PM -0700 >"Both traces are present, position works, sweep varies etc. " Excellent, now we can go from there. I am not an expert in scopes but I am, or at least was an expert troubleshooter. Each trace is controlled by the proper position control without abnormal interaction between the two. It shows both traces simultaneously in chop or alternate. If this is all true that means the output and the channel switching circuits are working properly. One question, relevant but not of prime importance, does you friend always use the X10 probe ? ALWAYS use the X10 probe unless you need the gain afforded by the X1 probe. this protects the front end of the scope and lowers circuit loading during testing. Since he cannot fix it himself he might not know this. Ask and tell when you get the chance. There is a chance that he actually caused the failure if the one channel in the past and then this channel now if he does not use the X10 probe(s). Regardless we still have a direction. there is a slight difference though, if he used the X10 all the time we are looking for a fault that just happened, if he uses the X1 we might be looking at something else. But that does not stop us in our tracks. You are going to need, at minimum a signal generator or a working scope to fix this. If DC voltages would reveal the problem most likely the trace would be off the screen on affected channel(s). Since it is not we are dealing with a dynamic situation, not a static one. The attenuator is not likely to develop a fault that would cause no response in any range, before it is suspect as is after. There is nothing active before the attenuator except the AC/DC switch which is easily tested. Then we have the possibility of him causing a low value resistor there to open either by excessive slewing in the input signal or overvoltage slamming against clamping diodes. That is eliminated with a signal generator. It is all high impedance so take a generator trough a 2K resistor to the portions of the switch and see if you get deflection. If so it is right up front, if not, it is after the attenuator. A 1 KHz square wave is usually sufficient. About 10 volts P-P should get a rise out of it. If it is extremely distorted though it is still after the attenuator. Then you need to find where the signal goes. If it is single sided PCB it is not all that hard. Point to point and multilayer PCBs bring in magnitudes of increased difficulty. But you can still look for identical components. Being Hitachi and not HP or Tak is actually an advantage here. It is likely that the parts are not house markeds and thus can be researched. Like to get the pinouts of ICs and the specs on transistors. And being Japanese, or at least conforming to their standard rather than JEDEC or whatever, on transistors the collector is usually in the middle. It is much eeasier to determone of it is BCE or ECB than the US way. Actuially some European standards are like those of the US, but Hitachi is usually going to be BCE or ECB, unless it is a really high frequency transistor in which case it could be BEC or CEB. If it is like a 20 MHz scope or so you can almost count on it being BCE or ECB. Too bad don' t remember my login for Hitachi from my working days. If I find it I will get the print and somehow supply it, though I have no hosting right now. Maybe I could email it to someone who does or perhaps contribute it to BAMA or some other free file place. But for now we must do without. So now, look for the switching circuit as well, it will have at least 4 diodes per channel, high speed and it will be directly before the main vertical output amp. the generator with the resistor may help. Always use the resistor because otherwise you might cause further problems. And be on the lookout for a very small result on the screen because some of the stages might be mainly current driven. that means low impedance. just be attentive. Get back here with a list of equipment you can use on this in the way of generators and working scopes and either their specs or model numbers. Don't reply via email. Put it out here so we can get input from others or perhaps help someone. I avoid doing this by email for those reasons. In fact I check this group more... I will watch for your response.The 2K value for the resistor is not etched in stone, 1K would do but... and 5K would do but... Just find out what you can. |
| jurb6006@gmail.com: Mar 17 08:31PM -0700 Oh, you are ot going to be able to do this yourself ? i forgot that part. It looks like your friend is in for some work and education. just forward all this to him and get his responses or whatever. How else would it get done ? |
| jurb6006@gmail.com: Mar 17 08:46PM -0700 Last but not least, those who say it is not worth your time, fukum. (well not really) They have no idea what your time is worth to you. They have no idea what your friendship is worth to you. They have no idea what new knowledge and techniques are worth to you. And, analog scopes are "the bomb" in contemporary vernacular. As you teach with one you slow down the sweep so they can actually see the trace move as you connect a battery, or a speaker output from an amp. I think the study of analog scopes should be mandatory in schools at least in the beginning when they learn the basics. If you can rig up simultaneous voltage and current sensing you can demonstrate reactance, power factor and all kinds of shit in real time. You can make them understand for real rather than just able to do the math. The young need this knowledge for all that is to come, and there is no better way to instill it. I will try to save almost any DC capable scope that has triggered sweep and a decent graticule. |
| Fox's Mercantile <jdangus@att.net>: Mar 17 11:47PM -0500 > Oh, you are not going to be able to do this yourself? I > forgot that part. Phil and his scope are in New South Wales Australia. Most decidedly NOT on my bench. > It looks like your friend is in for some work and education. > Just forward all this to him and get his responses or > whatever. I forwarded you full response to Phil. -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com |
| John-Del <ohger1s@gmail.com>: Mar 18 06:26AM -0700 On Saturday, March 17, 2018 at 8:48:23 AM UTC-4, Fox's Mercantile wrote: > Jeff-1.0 > WA6FWi > http:foxsmercantile.com Not to impugn your friend's intelligence Jeff, but any chance he first had one and now two broken probes? Most of us would assume he'd try to swap probes after the first channel went out but... |
| jurb6006@gmail.com: Mar 18 06:51AM -0700 >"but any chance he first had one and now two broken probes? Most of us would assume he'd try to swap probes after the first channel went out but..." Impugn all you want, you are right. It is possible he only has two probes. Getting this down Fox's ? Stick something in the hole in the BNC connector on the scope and see if you get anything out of it. Sorry, I assume things like this have been eliminated but I have been burned a few times. A thin gauge wire on a resistor or cap will fit in there. If this has already been checked - disregard. |
| Fox's Mercantile <jdangus@att.net>: Mar 18 09:22AM -0500 > Impugn all you want, you are right. It is possible he only has two probes. > Getting this down Fox's ? Stick something in the hole in the BNC connector on the scope and see if you get anything out of it. Sorry, I assume things like this have been eliminated but I have been burned a few times. > A thin gauge wire on a resistor or cap will fit in there. If this has already been checked - disregard. They had the scope turned on while I was talking with them. No response to anything on the input BNC connectors. However, the vertical would "thicken" in response to the cell phone transmitting it it was close enough to the scope. I'll say it again, it looks like they killed something between the input connector and the vertical amplifiers. -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com |
| Terry Schwartz <tschw10117@aol.com>: Mar 18 07:44AM -0700 I love when someone declares himself an "expert". I've been in this field 40+ years and I learn something every day I work on electronics. I hope I am never so pompous as to consider myself an "expert". |
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