Using an old Telequipment D54 Scope to measure TG output

[Drawbar Dave]

I have an old Telequipment D54 Scope that I am messing around with. It’s an early transistor type. I’d like to know whether it is good enough to read the TG outputs on my BC’s generator in MvPP. I don’t want to spend money on an expensive Fluke multimeter if I can use the D54.

Here’s a link to the specs: https://www.radiomuseum.org/r/telequ...scope_d54.html

Thanks
Dave

[tpappano]

It looks to me like that scope will only give you a 1cm trace for a 10 mv signal, and lots of newer scopes won't do much better. My preference for measuring small signals is a (analog) Ballantine AC voltmeter, which I have always considered the 'gold standard' for this sort of thing. There are various models available used, I have two different ones that I think I paid about $10 for. These meters typically range down to 1 millivolt full scale, are accurate, dependable and have linear and db scale markings. I have a model 3015 and a 323. Unless you like to tinker, you might want to avoid the 323, while it is an excellent wideband instrument, it has an internal nicad battery which will surely need replacement and is essential to the internal power supply even when running off AC line power. Use caution if buying a digital multimeter for this task, they might not have the bandwidth to accurately measure the range of frequencies your TG generates. My Fluke 117 is only specified to 1000 Hz but my 8845 goes to 300 kHz. I notice there is a Ballantine 3046 on a certain auction site pretty cheap 8)

Disclaimers:

I just like old instruments, my lab is a 'working museum'! Buying something used can be a restoration adventure, new might be safer but check the specs!

[Jyvoipabo]

Hello,

Your D54 is a general-purpose oscilloscope that have a poor input sensitivity.

As a measuring device on the L series Hammond recommend :
VTVM millivolt commander 870
and the tektronix 503 or equivalent.
The 502 which is a dual beam with two 100µV differential inputs is also a very good choice.

But you can use your D54 by connecting it to the speaker terminals. It is a easy way to adjust the percussion and vibrato.

JP

[stefanv]

I used a scope set to 5mV/cm and it worked sufficiently well. At 10mV/cm (if tpappano is correct; I can't blow up the pictures of the scope you linked to), resolution will of course be lower, but it will get you calibrated much better than the organ is now if you have just recapped it. Even a 10% measuring error is less than 1dB.

[Drawbar Dave]

Is a fluke 117 or 87v good enough for tone generator readings in mvpp?

[4hammonds]

yes it is, i happen to have one ( fluke 87v) and i used it when i recalibrate my A100
nice meter by the way!

[Drawbar Dave]

Thanks I also found a fluke 179

[tpappano]

I just checked my 117 on a 10 mv signal from 20 Hz to 10 kHz, it does read accurately.

[Drawbar Dave]

yes it is, i happen to have one ( fluke 87v) and i used it when i recalibrate my A100
nice meter by the way!

I found an 87V at a good price. Looking forward to taking readings from my BC as soon as the meter arrives. I am not going to recap, just take readings.

I’m also interested in taking capacitance readings on the cardboard tubed wax caps to see how much drift there is.