Curve Tracer

[jackinnj]

As I said a few posts back, don't purchase a curve tracer without either 1) playing with it yourself to make sure it works, or 2) purchasing from a dealer with a decent return policy. You might want to query the TekScopes Yahoo group for more advice. You can search the message archive for info.

The 576 is capable of higher currents than the 577.

[smoking-amp]

I bought a Tek 576 off Ebay a few years ago and modded it for tube testing.

The main problems I had were the rotary switches being flaky. These operate via cam rollers that depress spring contacts onto gold plated PCB foils. The higher current contacts had burned small holes thru the foils. Particularly the ones operating the readout bulbs, but there are others too.

I was able to fix this by some very delicate surgery. Either heat up the solder holding the springs to move them slightly with tweezers or bend them slightly. Tricky to say the least. But patience paid off. These cam switches are also very susceptible to dust getting in them and causing opens. The contacts don't slide.

The other issue would be to check the CRT for burn spots around the lower left 0/0 corner. And check for cracked knobs.

One nice thing about the 576 is it has an internal hidden option for external Vertical or Horizontal signal inputs. Was used by one of the upgrade DUT plug-ins. I just wired the inputs to some BNC connectors. Now I can monitor tube screen grid current or Mu easily with some external current or V probes.

[tommy1000]

Thank you.

[paulxbe]

Hi Peeps,

Just a quick support for the comment about the Curve Tracer (advanced).
I produced one based on this, and added MOSFET mode as well, I originally built it to characterize some FETs for an audo oscillator.
If I ever see the CT for my 7k mainframe at the right price I will probably grab it as well, and a 7L5 )

Cheers

Paul

[Sendy]

Originally Posted by smoking-amp

One nice thing about the 576 is it has an internal hidden option for external Vertical or Horizontal signal inputs. Was used by one of the upgrade DUT plug-ins. I just wired the inputs to some BNC connectors. Now I can monitor tube screen grid current or Mu easily with some external current or V probes.

PLS grid current - how most sensitivity range your modded CT have ?

[smoking-amp]

"PLS grid current - how most sensitivity range your modded CT have ?"

The external inputs (using the 10X magnifiers on) on the 576 appear to have 2.5 mV/div Vertical sensitivity and 5 mV/div Horiz. sensitivity. I use a Tek AM503/A6302 DC current probe unit with it to sense currents, which has 1 mA/10 mV out lowest range (using a 50 Ohm cable terminator, but can get about 2x sens. without the terminator, not Cal'd then). So should give .25 mA/div Vertical (with terminator) or about .125 mA/div Vertical (no terminator). There is significant noise in the signal at such high sensitivity though (5 MHz or 50 MHz BW available on the AM503) , but a low pass filter (RC) will fix that for Curve Tracer use.

[Sendy]

Thanks. AM503 is a good idea.

[paulxbe]

Hi Sendy,

The brief spec is as follows

Collector current limit 7 to 80 mA adjustable
Collector voltage 20 to 80 in 4 steps
Base current steps 2 uA to 1mA in ranges
Gate drive steps 0.1V, 0.5V, 1.0V

Modes BJT, JFET, MOSFET, Nor P polarity

Xoutput 100mV/V . Youtput 0.1V/mA

It fun to drive, but I am still looking for a 7CT1N )

Cheers

Paul

[Loudthud]

Originally Posted by jackinnj

The 576 is capable of higher currents than the 577.

The 576 and 577 both go to 20 amps. The difference is the 576 collector supply is 15V at 20 amps, the 577 is 6.5V at 20 amps. The 176 Pulsed High Current plugin "front porch", which only works on the 576, can do 200 amps at 15V, 40 amps at 75V, or 8amps at 300V. There was a high current option for the 575. It was a big transformer that sat on the floor and weighed maybe 100 pounds. The 577 had a plugin that tested op-amps. But nobody here uses op-amps, right?

[jazbo8]

I don't want to start yet another thread on curve tracers, so I will just piggyback onto this one, since the discussion is relevant still. Since none of the older curve tracers can be interfaced with the PC, and are bulky, heavy and full of obsolete parts, why get one?! With that said, I still want one, can some one talk me out of it!

Jaz