Tech TE-20 Sig Gen

[stitch1]

Hi Martin,
Thanks for your interest ... bit of a late night last night but I've got some time today so I'll get sorted and take some readings ...

John

[6AL5W-Martin]

Testing Voltages, with a trustful Fluke, all results from a warm TE20

AC secondary Voltage from Trafo: 121V
DC at Elko1 10µF , kathode from rectifier: 144V
DC at Elko2 10µF behind the 2K: 106V

(144-106)/2000 = 19mA current at the 2k resistor.

[stitch1]

Ok so I’m getting the following readings with MOD on external and RF out MAX.

A 120=117.5//300=309.7
B 350=348.5//1000=1008
C 1000=9826//3000=2936
D 3500=3451//1100=1087
E 0 or 5Mhz intermittent
F 0

I understand from Torbens post #11 above that F is not configured on this model.

I’m using a DMM for the readings. And this is the waveform.

John

PS I’ll do the V readings now

[6AL5W-Martin]

make always OFF the modulation to count the outgoing frequency.
The very best signal is a not modulated sine.

Please compare the 144V and the 106V, so we know the current. A low current is mostly a tired tube. A swimming 106V is mostly a tired Elko 10µF
About the high frquency counts, I am not shure if your multimeter can count so fast.
Otherwise control that with a radio
put a single cable in the red out from TE20 as antenna, the radio have to find him.

Your Range D: going to 11.000kHz = 11Mhz (shortwave)

[stitch1]

Yes modulation is off

Voltage readings are in ...

AC secondary Voltage from Trafo: 121.5V
DC at Elko1 10µF , kathode from rectifier: 134V
DC at Elko2 10µF behind the 2K: 100V

17mA current at the 2k resistor.

John

[stitch1]

For my understanding could you post a picture of the waveform with and without modulation?

Thanks

John

[stitch1]

Originally Posted by 6AL5W-Martin

put a single cable in the red out from TE20 as antenna, the radio have to find him.

Your Range D: going to 11.000kHz = 11Mhz (shortwave)

I'm sure I have a radio around here somewhere I'll set something up now

[stitch1]

Range D is ok (see #23) range E had no reading and your assumption about the DMM is correct.
Using a SW rx’er:

11=10.74//25=24.25 (rx’er does not go to 35)

John

[6AL5W-Martin]

300kHz
3MHz
15MHz
28MHz
modless ripple

The amplitude form of this TE20 seems to be worst case by manufacturing
and at 28MHz the signal level is down under..
modulation do not make that better or badder .. last pic: ripple

we can watch a spectrum analyzing if you like also.

[stitch1]

Thanks for your help Martin.

Just to recap (no pun intended)
Going back to the original issue where there was no modulation I now have modulation and I can demonstrate this using another radio and switching form INT to EXT MOD.

The frequency ranges are more or less accurate and I can work with the small error when aligning my radios.

So what's changed?

Changing the capacitor on the anode of V1 meant I now had modulation although the frequencies were inaccurate and changing the other 1500pf capacitor (on the left) seems to have rectified this and I'm now getting reasonable accuracy accross bands A to E.

I think we've done all that can be done and I can get back to the radio alignment I was doing, unless I've missed something?

John

[6AL5W-Martin]

I think that is ok so,
but I wonder about only 134V there after the rectifier.
In my TE20 there are 10 Volts more. Is the first 10µF leaky? Or is the rectifier another, I see here 1N4007

[stitch1]

Thanks Martin, whilst it is apart I may as well check, I'll double check my readings and do some tests.

John

[stitch1]

I checked the voltages again and they were the same so I changed the rectifier, no change. there didn't appear to be any leakage (mVs) on the capacitor but I temporarily replaced it to be sure, again no change.

I'm happy with the progress and I'll try some alignment and see how it goes.

I really appreciate everyone's help and input I've enjoyed working on this.

John

[See_Mos]

Interesting, my Eagle TE-188. In need of a clean but works OK

[David G4EBT]

Originally Posted by See_Mos

Interesting, my Eagle TE-188. In need of a clean but works OK

If you have a 'scope, what does the unmodulated waveform look like? Both John's in post #13 and Martin's (at 300kHz and 3 MHz) in post #29 show a distorted unmodulated sine wave, though Martin's looks undistorted at 15Mhz & 28 MHz. Probably doesn't matter so long as the frequency is accurate. Not that it's any relevance, I prefer the TE20 front panel layout to the later TE20-D.

[See_Mos]

The wafeform becomes more pure and the amplitude reduces as frequency increases.

Scope is 20MHz HM204-4

[ms660]

The waveform looks normal for a grid leak special with no automatic level control.

Lawrence.