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When I repaired my 8645A some years ago I noticed a very sluggish user interface whenever the PLL unlocked. I guess repeated unlock signals did continuously interrupt the CPU to produce that effect.

Thank you all, very useful. Factory, I will replace all power supply paper capacitors, and thanks about checking that the values didn't change for all serial numbers. The cap values should be to a

Dear Yves, Thank you for the comparative measurement, showing noise from the 8657B in RF Off being 4.6 dB above thermal noise. The difference I measured is somewhat less, because I did not correct

Hello All, Thanks for your help! We finally solved the problem which was caused by the OS which was corrupted. Br. Antoine

Btw I did get hold of Julio and he confirmed that there is a mix of 27C512 and 27C256 chips on the 4.22 ROM. Unfortunately he cannot read the EPROMs from the unit as he no longer has any windows PC to

Maybe some else wants to install the 4.22 roms and check ?

I don't think I'm misidentifying the hoofbeats as zebras. I'm perfectly willing to admit that I may have missed something, and I really hope that I have, because that means there's really no

The carbon composition resistors were probably used with the thought that they are rugged, and will only introduce a variation that is less than system noise. However, carbon composition resistors

Hi Dave, I can't help it, when you say stuff that sounds like you are missing something simple, I am going to try to help you as politely as I can. We all make incorrect assumptions, and we

Well damn, now I'm really looking forward to it. I wish I wasn't so damn busy this week. I'm shipping prototypes of a new design to an absolutely neurotic client next week. :-/

Jared, A couple of points: - Please make sure you account for your 731B's own tempco, which typically is not negligible. I have one that's unusually stable, but most units exhibit quite a

I am seeking some help with my HP 8566B which has a PL2 unlock error. While I understand the use of the instrument, I need some guidance in fault finding. The error occurs when the span is increased

Thanks for the replies. I am inclined to leave the resistors alone, but I just keep wondering how much their temperature coefficient and value drift with age would be affecting the accuracy of the

Yes Chuck, I know how EPROMs and EPROM programmers work. I've been using them as long as you have. I think we're talking past each other. There's something up with the 3852A EPROM images, as you

I'm not suggesting that at all. If you read a 27256 in an EPROM programmer set for 27512, you will get two copies of the 27256, one in each half of the 27512. I'm suggesting that an EPROM usually

Alwyn, I set the frequency of the 8657B to 2GHz, RF OFF: the noise floor at 450 MHz was -163.3dBm/Hz (yellow trace). Terminating at Spectrum gave me -167.9dBm/Hz (blue trace). Yves De

On Wed, May 8, 2024 at 03:27 PM, Bepi wrote: > > I found the main power supply issue, a blown capacitor in the HV section, > one side to ground. Unplugging the tubes was not enough to exclude the

Very nice work indeed! Thanks for making such careful measurements. That data is pure gold. -- Cheers Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 420 Via Palou Mall Stanford University Stanford,

Where Julio bought his programmer, where it was built, which one it was, or what OS he was using to drive it has no bearing whatsoever on the size of the EPROMs or the correctness or lack thereof of

Dear Yves, Thanks. For the measurement I tuned the 8567B to a frequency far from the 450 MHz measurement frequency- above 1,200 MHz. The measurement was made using a low noise (around 1dB Noise