Klemt Echolette S...(cont.)

[solymosilev]

Thanks for the answer. Yes I have replaced the bridge and all power caps to 4x47MF. No hum at all.
Yesterday I had a short test with a new tape and it seems that the unit is okay.
One interesting thing is that the "magic eye" which is about a half millimeter slice without sound. If I play music at maximum peak, it only widen to about 3 millimeters not more.
Is there any trimmer pot to adjust the "magic eye" circuit signal input? Or the tube is faulty?

https://www.youtube.com/watch?v=6O0G-LsTk6Q

[Mickey]

There is no adjustment and the tube is not faulty.
As I said in my last reply you should replace all those small capacitors..0047, .022 etc
Which model do you own, does it have a printed circuit board or are the small parts wired to tag strips, there are some differences in the circuitry and the ease in which components can be replaced.

[solymosilev]

Hello Mickey,
I have the one, with circuit board. Yes it would be nice to replace all caps. but i guess I will not dis-montage the unit.
I fear that some or more wire will break (as I experienced already during fault analysis).
So now the unit works and does its function as expected after 50 years.
Thanks,

[Sin1949]

There is no adjustment and the tube is not faulty.
As I said in my last reply you should replace all those small capacitors..0047, .022 etc
Which model do you own, does it have a printed circuit board or are the small parts wired to tag strips, there are some differences in the circuitry and the ease in which components can be replaced.

Hi Mickey,
I have noticed that you are an expert for repairing Echolette NG51S echo units. I have an Echolette NG51 S my model is with a printed circuitboards, everything works perfectly, transportation system all five magnetic heads have 1.2 KOhm resistance a ‘Dry’ signal is crisp and without any hum, I checked two playback heads by gently teaching them with a screwdriver and they work, I can hear them via my guitar amplifier.

However, I cannot get any echo sound. I measured the voltage on the variable caps and I got low voltage result. Head 1 has 20 Volts, Head 2 had 30 Volts and Head 3 approx 44 Volts all voltages have 65KHz frequency. The erase head has only 20 Volts!?

Is it possible that the high friquency oscillator is not working or should I check something else?
Thank you in advance,
Sinisa

[Helmholtz]

However, I cannot get any echo sound. I measured the voltage on the variable caps and I got low voltage result. Head 1 has 20 Volts, Head 2 had 30 Volts and Head 3 approx 44 Volts all voltages have 65KHz frequency. The erase head has only 20 Volts!?

Is it possible that the high friquency oscillator is not working or should I check something else?

I'd say 65kHz is your oscillator frequency, so it's working.

I guess you used a scope for the measurements?

Are all switches working properly?

[Sin1949]

Hi Helmholtz,


Yes, I used a digital scope and high quality Fluke multimeter and I got 65KHz oscillator frequency measuring on the three variable capacitors connected to recording heads.

I know that the voltage on the recording heads should be in. the range of 40Volts for Head 1, 70Volts Head 2 and 90Volts for Head 3.

So my question is: Let say, consider that the high frequency oscillator is working how to bring up the Voltage on three recording heads? Also I checked the ECC82 oscillator tube and it is working properly.

All the switches are working properly.

[Helmholtz]

Where do the reference HF voltages come from?

Are you sure you're not comparing RMS values with peak-to-peak values?

Did you ever measure your HF voltages before this failure?

[Sin1949]

I measured the Voltage/Frequency at the three variable capacitors located at the right hand side of the chassis looking at the face plate of the echo unit. I did not measure Voltage/Frequency before.

Also when I connect the echo unit with the guitar amplifier and when I am touching the connectors of those three variable capacitors I can hear a sound (screeching sound) from the amplifier. That is telling me that there is some ‘life’ connection between the variable capacitors and echo unit exit.

[Helmholtz]

Please answer my other 2 questions above.

I'm not convinced that the HF levels are your root problem.

[Sin1949]

Please answer my other 2 questions above.

I'm not convinced that the HF levels are your root problem.

I measured the Voltage directly from the variable capacitors which is the RMS Voltage.
At least I think so, as I remember that the Peak Voltage should be calculated by formula 2x square root of RMS

[Helmholtz]

I measured the Voltage directly from the variable capacitors which is the RMS Voltage.

How do you know?

A sine voltage can be specified as RMS value Vrms, peak value Vp = 1.4 Vrms or peak-to -peak value Vpp = 2 Vp = 2.8 Vrms.
DMMs typically measure RMS value.
With a scope you typically read Vpp.

HF voltages in schematics/manuals are often specified as Vpp.

So again my question: Where did you find the reference HF voltages? Can you post your source?

[Sin1949]

How do you know?

A sine voltage can be specified as RMS value Vrms, peak value Vp = 1.4 Vrms or peak-to -peak value Vpp = 2 Vp = 2.8 Vrms.
DMMs typically measure RMS value.
With a scope you typically read Vpp.

HF voltages in schematics/manuals are often specified as Vpp.

So again my question: Where did you find the reference HF voltages? Can you post your source?

So, here I am again I checked again the Voltage/Frequency using my digital Scope.

The frequency was 57.3KHz at the Head1 the Vpp = 101.56Volt; Vmax= 50.6Volt and Vmin= 50.9Volt
Interesting the same Voltage/Frequency I measured on the H 2.
However, I am sure that the Voltage on H 2 I can fine adjust to different values.

[Helmholtz]

The frequency was 57.3KHz at the Head1 the Vpp = 101.56Volt; Vmax= 50.6Volt and Vmin= 50.9Volt
Interesting the same Voltage/Frequency I measured on the H 2.
However, I am sure that the Voltage on H 2 I can fine adjust to different values.

These values don't look consistent with your earlier measurements.

Some more info here: https://music-electronics-forum.com/...tte-klemt-ng51

Judging from the variable cap values HF bias should increase from head 1 to head 3.

But I don't think wrong HF voltages are the reason for your missing echo sound.
So you need to do real troubleshooting.
Start with measuring tube DC voltages and post them.
Then feed a 100mV/1kHz signal to an instrument input and trace it to the record level controls.

There is useful info earlier in this thread.

Be prepared to replace a tube.

[Sin1949]

These values don't look consistent with your earlier measurements.

Some more info here: https://music-electronics-forum.com/...tte-klemt-ng51

Judging from the variable cap values HF bias should increase from head 1 to head 3.

But I don't think wrong HF voltages are the reason for your missing echo sound.
So you need to do real troubleshooting.
Start with measuring tube DC voltages and post them.
Then feed a 100mV/1kHz signal to an instrument input and trace it to the record level controls.

There is useful info earlier in this thread.

Be prepared to replace a tube.

Thank you for the quick response. Yes you are absolutely right, the results are not consistent because in the mean time I have adjusted/tuned the variable capacitors and the trim resistors. Also I used then my old analog Tektronix 2212 scope and Fluke multimeter and I got obviously the half of the Vpp.

But I will change the Voltage setting and now I am using Hantek Digital scope which is reading automatically the Voltage and Frequencies.

As I know the HF bias should be be 60Volt at H1, 90Volt at H2 and 120Volt measured at H3.
The erase head should be approx 70Volt.

Tonight I will measure all the points that you mentioned. Soon after I will post the results.
Best Regards from rainy Vancouver, BC, Canada

[Helmholtz]

As I know the HF bias should be be 60Volt at H1, 90Volt at H2 and 120Volt measured at H3.
The erase head should be approx 70Volt.

I already asked several times: What is your source? And are these Vpp or Vrms values, as the difference would be almost a factor of 3?