I am restoring a Triplett 3433 and have replaced some capacitors and replaced some resistors increased in value, but still have a problem. I do not seem to get the oscillator freq out of the RF output connector. The oscillator is functioning because with the chassis out of the metal cabinet, I can follow the freq with a near by radio receiver. I suspect the 6SA7 RF amp/mixer. However, I want to confirm that I am not getting sufficient output from the RF connector. Therefore, my question is: what voltage should I get when I put my digital AC meter on the RF output. I get about 30mV.

Most digital meters are very limited as far as Ac frequency measurements go. You would really need a scope to see the output. There could be a problem with the attenuator but usually you will see a burned out resistor causing the problem.

Lou,

Thank you for your response. I have solved the problem and you were absolutely correct. First, the Amprobe digital meter is great, but not suited for measuring the oscillator output without loading down the circuit. I put my PicoScope 3205B on the output and it is right on the money. I had resolved all issues without knowing it after having replaced my last resistor. I had been using my scope the whole time, but got lazy at the last stage and tried to use my digital meter out of convenience. This is a really nice signal generator and I am very glad to have it operational.

Thanks again!

Steffen

It seems I am not done yet!

I have a follow up question. I know it is a stupid question at this point in time, but here it is. The Triplett 3433 has a "MULTIPLIER" multiswitch, an "RF UNITS" potentiometer and a "METER ADJ" control under the RF Output meter. What is the function of each?

I assume that the multiplier (X1, X10, X100, X1M, X10M, HI) is a rough setting for RF level of the output. The rf units pot (0-5) seems to me like it would be a finer granularity adjustment within the multiplier setting. Finally the meter adj (0.1-0.3) is just a way to get a reading on scale for whatever values you have set the other controls.

I am asking this because now that I have the replaced the resistors in the multiplier, I get output from the "OUTPUT" rf jack, but not on all of the multiplier settings. I get output on the "OUTPUT" jack for all frequencies when set on the X1. For example, if I set the freq range to 400-820 kc and the dial to 580 kc, that's what my scope displays as well. Once I put the multiplier to X10, etc. the scope displays frequencies around 90Mhz - this is just noise. If I put the multiplier on "HI" then the frequency from the "HI" rf jack is always correct.

I replaced everything in the multiplier switch assembly and believe to have wired it correctly, having rechecked several times.

All comments will be highly appreciated. Thank you.

The signal generator is now working. I came to understand that the multiplier is a T attenuator used to maintain a stable amplifier load and output impedance. It can also offer more isolation. Using an ohm meter, it is logical that I would see similar resistance readings on all switch settings, and that resistance reading would be the expected load impedance.

My problem was three-fold. 1 - I did not have a full understanding of the purpose of the multiplier circuit, 2 - there is a missing external load selector circuit, and 3 - I had inadvertently swapped the LO RF and HI RF output jack shielded cables when placing the assembly back in the signal generator. The latter mistake only further confused the matter. The missing load selector circuit must have been in a probe or external housing. Once I connected a .047uf capacitor to the LO RF output jack as a test, the scope displayed the signal as expected - in all cases.

The multiplier circuit is the following:



The multiplier assembly is boxed in blue, the missing output load selector is boxed in green and the swapped output jacks are circled in red.

I am sorry that I may have caused you to waste time in analyzing my questions. It was due to my lack of understanding of the T attenuator's purpose. I am very happy to report, however, that all is working just fine now.

Thank you all again!