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Anyone know if there is an equivalent for this Tek part number, listed in the TG501 parts as 'Hot Carrier, 4V' ?
It's used as a frequency multiplier to generate the 1nS markers from the 2nS signal. My TG501 has working markers down to 2nS but no signal on the 1nS output, so it would appear the diode is faulty.

On Mon, Jan 27, 2025 at 08:22 AM, Keith wrote:

Hot Carrier,

152-0536-00

CR515 152-0536-00 SEMICOND DEVICE:SILICON,HOT CARRIER,4V 80009 152-0536-00

Appreciate that Miguel but that's for 33, I just need 1!

Since it's being used as a frequency multiplier, I expect it's a step-recovery (snap-off) diode. If I had to improvise, I'd try a varicap diode because I heard that they have some step-recovery behavior.

FWIW,
Dave Wise

________________________________
From: [email protected] <[email protected]> on behalf of Keith <keith@...>
Sent: Monday, January 27, 2025 9:32 AM
To: [email protected] <[email protected]>
Subject: Re: [TekScopes] 152-0536-00 hot carrier diode

Appreciate that Miguel but that's for 33, I just need 1!

wich scope are you using to see the 1ns pulse?, I think that you need a 1ghz scope if I recall correctly. I have a TG501, with a 500Mhz scope (TDS5054) I don?t see the 1ns pulse, but with the 7s14 it works.

Using a 1GHz scope (RTM3000) which should be able to see it.

I'm wondering if it is CR515 or something else. If I measure the amplitude (Vpp) I see:
10nS - 1.480v
5nS - 0.820v
2nS - 0.724v
1nS - noise (10mV or less)

I'd expect the 5nS output to be similar to the 10nS (and slower) markers?

On Tue, Jan 28, 2025 at 05:13 PM, Keith wrote:

I'm wondering if it is CR515 or something else. If I measure the amplitude
(Vpp) I see:
10nS - 1.480v
5nS - 0.820v
2nS - 0.724v
1nS - noise (10mV or less)

I'd expect the 5nS output to be similar to the 10nS (and slower) markers?

Hello Keith,
You don't mention which RTM3000 you're using. They start out at 100MHz bandwidth but from your amplitude info, I guess that's not your model...
Do you have a TG501 service manual?

I haven't experienced nor read about a failed CR515.
It has always been (one or a combination of) expecting to see the 1ns pulse on - say - a 100MHz BW 'scope, incorrect filter adjustment, not using the correct (1ns only) output of the TG501, trigger problem, bad/intermittent contacts on the PCB, leading to incorrect filter adjustment. The 1ns adjustment has a big influence. Maybe someone using the wrong 'scope has been in there before you?

I just checked one of my TG501's

On a Tek 7904/7A19 (500MHz nominal BW):
10ns 1.5V
5ns 1.1V
2ns 0.9V
1ns 50mV

On a Tek 7000/S-4 sampling 'scope (<=75ps nominal rise time):
2ns 1.05V
1ns 0.35V

If no other explanation, try filter adjustment, following the service manual. It's not difficult, *if* you have the right 'scope...

Raymond

BTW the pulse amplitude specs are on page 1-1 in the Service Manual. TG501’s I’ve seen easily meet those specs.

Raymond

Hi Raymond,

Yes I'm using a 1GHz bandwidth scope at 5GS/s. I've also tried looking at the output on a spectrum analyser, seems the largest peak is at 800MHz with many other harmonics of 200MHz/5nS.

I am thinking you could be right, someone's maybe 'got at' this unit and tried adjusting the filter and made it worse... I'm going to make up an extender board so I can try adjusting it as per the service manual.

- Keith

I've put in the folder 'TG501 2ns and 1ns spectrum' plots from the TG501 for both the 2ns and 1ns outputs. The latter is clearly faulty...

My TG501 at 1nS with a 7s14

/g/TekScopes/photo/300311/3881197?p=Created%2C%2C%2C20%2C0%2C0%2C0

So I got some 1N5711 small signal Schottky (hot carrier) diodes.

Getting to CR515 in the TG501 is tricky, first you need to remove the metal shield on the top of the PCB, which is held in place by small screws. But you find the diode has been mounted flush with the stripline, and the back of the PCB has another metal shield that is not easily removable without damage.
I resorted to cracking the diode with a pair of sidecutters, and soldered the new diode in carefully to the existing pads.
Put the shield back and powered up and... nothing on the 1nS output.

At this point I started twiddling the trimmer caps of the 1nS filter, in the order the manual describes. First one had no noticeable effect. But the second one showed a bit of a signal at 1GHz. The trimmers are incredibly fussy, in particular the 2nd and third ones, a very small movement can cause the signal to drop 50%. After looping through about a dozen times I managed to get ~60mV output of a clean 1GHz sine wave. So maybe the diode wasn't bad, maybe a previous owner had got at it, who knows. The voltage I'm getting seems to agree with Raymond's, which is good enough, even if it's less than the 200mV the manual says is the target.

The 2nS output benefited from a little adjustment too and is giving out a healthy 1.2v signal now.

- Keith