An update on the
hp 180A I acquired last month.
The same weekend as the start of my computer malfunctions, the 180A decided it also wanted to play dead after I cleaned the beam finder switch.
Luckily it turned out to be a simple problem, the CRT socket was loose and must have only just been making contact to power the heaters when it first arrived, also found the hose clamp not tightened at all.
Onto changing the two leaking/corroded 40uF 30V wet tantalum capacitors (Sprague 109D) C327 & C328 in the 1821A timebase.
The best I could find in my stock were some NOS Philips 030 aluminium electrolytics rated at 47uF at 40V, every tantalum I had was too big to fit in the available space. The Peak ESR was used to check them & they tested better than the original parts.
After changing those I re-tested the 180A with the 1801A/1821A it came with and finally had a chance to test the 203A bread warmer from a few weeks ago.
The 203A is functional, but the coupler for the variable capacitor is broken, I wedged it in a fixed position to try it. Also the tuning dial mechanism needs a complete strip-down to be re-lubricated.
When I went looking for another signal source, to carry on with fault finding on the 180A trigger problems, I noticed a set of 1801A/1824A I had completely forgotten I'd bought. I gave those a test and found that they trigger OK, but only channel B is working on the 1801A from that set.
Radio Wrangler on the UKVRR forum kindly sent me the missing plastic CRT bezel for the 180A.
Today I had a little time to carry on with diagnosing the trigger problem with the 1801A/1821A set the 180A came with. I went through part of the adjustment procedure for the main & delayed sweep using the external inputs, TP204 & TP404 were both out of spec at 1.6V & -0.4V, they were adjusted to within 15mV of 0V using R238/R422. There was nothing wrong with trigger symmetry and I stopped at this point as the other adjustments are not trigger related. Strange how the tests in the manual only use the external trigger inputs.
OK that leaves two more possibilities for the internal trigger problem, the internal trigger amplifier in the 1821A, or a lack of a sync signal from the 1801A. At this point I decided to swap the 1821A timebase for the known working 1824A, that now also displayed the same lack of internal trigger. Next weekend I will have to go through the sync board on the 1801A.
David