I spotted a 547 on Ebay last night. Might fit the bill? Item 200618872943. Kevin

Ahh, good point. I should try that. It feeds the next stage through a 10k resistor so unlikely it's being dragged down but you never know... Yep, the thought crossed my mind too. Actually, the H&V cou

Hi Guys, I wonder if anyone has ever troubleshooted display issues with a 1240 Logic Analyser? Symptoms are that I get a stable raster on the screen if brightness is turned up but no display. All powe

I would fix the intensity problem first if I were you.Running the tube as bright as it looks in those pictures for any length of time will do it no favours at all. Check over all the components in the

Yep, that's it. You can regard it as a network that turns the Z axis signal (let's say it varies from 0-100V for the sake of argument. I'm not sure on the exact range) into an AC signal with an amplit

Hi Bryan, In addition to the excellent suggestions already made, if the cathode is OK at about -2KV I would have a careful look at the DC restorer circuit that drives the control grid of the tube. I.E

Well, I found the problem. U1909 had what appeared to be an internal short from the +7.5V supply rail to some of the output pins. Everything was fine until the range changes started to switch in the A

Yep, I've come across the dreaded increasing resistors before! I think I measured those two correctly but will double check. I will do, although I got the scope on the collectors of Q1910 and Q1911 an

The CTM runs through a series of checks at power-up and reports an error code if anything fails. Otherwise, it just enters normal operation. There is a good description of the self test and further di

I think I might be getting somewhere. Wind up the voltage slowly (so the Hi-Z buffer output only reaches 0.5v or a little more) and on some of the ranges the +7.5v is getting pulled down by a volt or

Hi Jim, Many thanks for the help. The switches checked out OK. I tried it with c1811 removed just for good measure in case the input amp. was overshooting and there was no difference. Incidentally, ap

Hi Guys, Does anyone have any experience with the DMM on the 2236? I have currently got my 2236 apart for another repair which has been successful. While I had the lid off I thought I'd fix a niggle I

Mine exhibited a similar problem once and the culprit was a group of 4 series connected 510k resistors in the dropper chain that fed the focus control. These run a little hot and one had failed. Kevin

I had a similar problem with my 2236 a while back. The switching transistor (from memory, a MOSFET on a heatsink just behind the cooling fan) had died. The fan had also seized up so I suspect it proba

I appreciate that, Chuck. Since I have a spare core sitting around anyway it is probably a no-brainer to turn it into a known good spare while the opportunity exists. Kevin

I'd be interested to know too. As it happens I came across a replacement HV transformer for my 546 on Ebay last week and it appears to be a good one (was dated 1972 IIRC). Chuck's post is quite timely