- TIP: Making connection to 0.5mm spaced lands/conductors. - 1 Update
- Marantz Model 19 Scope - 7 Updates
| N_Cook <diverse@tcp.co.uk>: Apr 29 04:19PM +0100 A much better solution , I picked up some surplus new of these "gigabyte 12CF1-1id133-61r" computer cables. .025 inch spacing cable for 0.1 inch headers , as inter-line ground wires and extra bridging IDC prongs inside the headers. Anyway ribbon is 0.635mm spacing with proper copper conductors (so heavy to the handling) , so its quite easy to strip off the insulation, at an end, after unclamping an IDC. Solder a 5 way strip at a time , as not 0.5mm spacing and add lacquer insulation afterwards. |
| jurb6006@gmail.com: Apr 28 12:03PM -0700 Thanks, it might help. However the tube socket is wired to a set of wires that do down to a socket on the board. There is no way to tell for sure the connections aren't changed from what you would get straight at the base of the tube. I haven't found a decent page on the CRT in the manual, in fact it says something like "provisional" as if they weren't quite sure whose tubes they going to use. Having the pinout, even in low resolution is better than nothing. |
| jurb6006@gmail.com: Apr 28 12:12PM -0700 >"I've been dealing with a slightly similar problem myself... I bought a CTS service monitor whose scope is working-but-dim. Fortunately it has a 3RP CRT (like the Cushman and Macintosh systems do) and I have a local source for a used tube (and there are online sources as well). " Have you tried boosting the filament voltage ? For one it is the best way to extend the life of a CRT, rather than rejuvinating. I wouldn't recommend that for a CRT unless it was in a TV, the color CRTs pull quite a bit of current and guess where it all comes from - the cathodes. But scope cathodes don't get loaded heavily. they can be just as bright as a tube pulling 20 times more current easily because they are not generating a raster. If it turns out to be weak emission in this tube I am not exactly sure how to boost the filament voltage. It seems to run off a resistive divider, but for a small tube which is a RAY type tube not a raster type it is sufficient. But then doing anything in that circuit might do something to the G1 bias or whatever. Thing is also figuring out how to actually test the thing if/when all the other possibilities are eliminated... |
| jurb6006@gmail.com: Apr 28 12:16PM -0700 >"shango66 on youtube does some good explanations re CRT emission problem fixing. Though I don't remember him discussing EHT boosting. " I'll have to look into that. Nobody in their right mind would try to save an old CRT by boosting the main accelerating voltage. First I will try the grid bias, if that does it fine, that is IF that is the problem and it isn't some other fault. Thing is I just heard from the customer that he scope used to work, he actually found the burning -500 rectifier. There are no shorts currently, the new rectifier is doing fine in there. But no trace. |
| jurb6006@gmail.com: Apr 28 12:45PM -0700 >"** Monochrome CRTs and monitors operated with HT voltages in the range of 16 to 20kV and were made with plain glass while colour CRTs operated at voltages about 5 or 6kV higher and were made with thick leaded glass at the face." >"The reason was X-ray generation." I believe that for whatever reason they started using barium for that. That was from a CRT rebuilder. We had, after the tube days, a new rating on CRTS, bars. On the bell of the tube there were either one, two or three bars right in the glass. the three bars were the only ones we could legally use in most of the newer delta gun sets. The older ones would work but well, we use the three bar tubes when called for. When they got to inline guns, even the original GE ones, (Sony was still first) they all has three bar glass. If I remember correctly the three bar tubes were good up to 35KV. >"However, seeing small kids sitting less than a metre from colour CRT screens always made me cringe." Kids here more like ½ metre. I wonder what the physiological effects could have been. Well, it seems more people in my age group wear glasses but can we attribute that to that ? Not so sure. I remember them saying that Xrays dropped due to gravity, though I kinda doubt it. Maybe as much as any photon would but there is no evidence I can't find now that it is any more than that miniscule drop. But they sold people on floor model TVs with it. Actually thing about it is I would rather have a TV at or below eye level. In fact people have their monitors set at an upward angle which reflects more ambient light. I avoid that but have found that some edge lit LCD screens like in laptops simply are not designed for that. Needless to say, this Xray shit is a hijack because this thing only has 500 volts. You get real Xrays out of that voltage maybe I will kiss your ass on public square and give you ½ an hour to draw a crowd. (no beans and no mooning) |
| tabbypurr@gmail.com: Apr 28 02:19PM -0700 On Sunday, 28 April 2019 20:16:35 UTC+1, jurb...@gmail.com wrote: NT: > >"shango66 on youtube does some good explanations re CRT emission problem fixing. Though I don't remember him discussing EHT boosting. " > I'll have to look into that. Nobody in their right mind would try to save an old CRT by boosting the main accelerating voltage. Well I've done it when all else failed, and it would not result in excessive x-ray emission. I kept one such set for 10 years or so, it kept going just fine. Why do you dislike it? NT |
| jurb6006@gmail.com: Apr 28 08:03PM -0700 >"Well I've done it when all else failed, and it would not result in excessive x-ray emission. I kept one such set for 10 years or so, it kept going just fine. Why do you dislike it? " Well you got lucky. High voltage components are particularly prone to failure even at their rated voltage and you may not have had problems, but I bet out of 10 times at least 7 would be a problem. Another thing is what did you do about deflection sensitivity ? How do you know it did not result in excessive Xray emission ? Piece of plywood and some photographic film in a dark room ? |
| tabbypurr@gmail.com: Apr 29 04:57AM -0700 On Monday, 29 April 2019 04:03:25 UTC+1, jurb...@gmail.com wrote: NT: > >"Well I've done it when all else failed, and it would not result in excessive x-ray emission. I kept one such set for 10 years or so, it kept going just fine. Why do you dislike it? " > Well you got lucky. High voltage components are particularly prone to failure even at their rated voltage and you may not have had problems, but I bet out of 10 times at least 7 would be a problem. There is a small failure rate at the original voltage. TV parts are generally run well below parts mfrs' rated voltage to improve reliability, eg 25kV on a 40kV part, 15kV on a 25kV part. Failure rate climbs as you apply more, but it only takes a small boost, 5-10%, and the increase in failures is not great for that much. But yes it's there. However the key phrase is when all else fails. 90% beats 0% by a long way. Cleaning the EHT stuff always helps, dirt degrades insulation capability.. > Another thing is what did you do about deflection sensitivity ? Raise B+ the same amount. In TVs the easiest way is just to raise B+ across the board. > How do you know it did not result in excessive Xray emission ? Piece of plywood and some photographic film in a dark room ? The OP has a 500v tube. Otherwise look up the datasheet for the CRT, they're often run below rated v. You can also use a counter. It can't measure all the tube's output, but it can measure background, and relative original & boosted outputs. Then you know what %age the increase is and can see if that's within requirements. NT |
| You received this digest because you're subscribed to updates for this group. You can change your settings on the group membership page. To unsubscribe from this group and stop receiving emails from it send an email to sci.electronics.repair+unsubscribe@googlegroups.com. |
No Response to "Digest for sci.electronics.repair@googlegroups.com - 8 updates in 2 topics"
Post a Comment