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Gonset G-50




 
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Author Topic: Gonset G-50  (Read 3279 times)
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PA0NVD
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Nico and Chappie (Chappie is the dog...)


« Reply #75 on: June 21, 2018, 03:21:45 PM »

Measure the voltages across the pot R54. One side shoud be approx 200VDC, the other side approx 80VDC
C65 at the 200VDC side may have shorted. that should give a dead receiver because the squelch is completely out.
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WB4YVO
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« Reply #76 on: June 21, 2018, 03:56:22 PM »

Ok Receiver not completely dead.. I get noise with the volume control.. Not as load as before .. The squelch works  I can mute receiver..

When it was working before pop.. The s meter was reading about a 2.5..  Now its reading a 1.. And volume is a lot lower.. and I could not Receive the Spot function anymore.. So I said Receiver was dead..

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PA0NVD
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Nico and Chappie (Chappie is the dog...)


« Reply #77 on: June 21, 2018, 04:54:56 PM »

Ok, that does change things. Lets go over the receive stage gains to find a low gain stage.. I did estimate some levels. Put a 10 pF in series with the signal generator and measure the following points. They should give approx the same signal strength +/- 1 - 2 S points Set the generator at 50% modulation.
V10, pin 1, 10 mV 455 kHz
V9, pin 7, 500 uV, 2.3 MHz
V8, pin 2, 25 uV, 2.3 MHz  and also 25 uV, 51 MHz
V7, pin 1, 3 uV, 51 MHz
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WB4YVO
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« Reply #78 on: June 21, 2018, 07:17:57 PM »

Ok here is what I get..

V10, pin 1, 10 mV 455 kHz    4  Good tone
V9, pin 7, 500 uV, 2.3 MHz    0
V8, pin 2, 25 uV, 2.3 MHz  and also 25 uV, 51 MHz   0,0
V7, pin 1, 3 uV, 51 MHz   0

V9, pin 7, 50 mv, 455 KHz    4  Good tone
V9, pin 7, 158 mv, 2.3 MHz   4  NO TONE

Skip..
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PA0NVD
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Nico and Chappie (Chappie is the dog...)


« Reply #79 on: June 21, 2018, 08:11:03 PM »

Seems that the 6BE6, V9, does not mix anymore, or very low level. measure with a scope at the cathode pin 2. There should at least be a few volts RF of the correct frequency, 2.3 MHz + or - 455 kHz (I do  not know if the oscillator is above or below the 2.3 MHz.)
First try an other 6BE6 V9
If no solucion
Pin 5 and 6 should have the same HV
When there is RF at the cathode, the oscillator is functioning, than the frequency of the oscillator is wrong. Most probable a bad soldering in the oscillator circuit.
Re-flow all connections in relation with the oscillator. If still the wrong frequency and very much off, the two tuning caps C30 and C64 may be off and should be measured, The value of these caps is important, otherwise there is no good tracking between oscillator and RF circuits when the frequency is adjusted.
If the frequency is just slighly off, you can try to change the core in L12, the oscillator.
BUT REMEMBER THE FORMER SETTING!!
When the oscillator is dead, measure from pin 1 to ground, should be 20 - 25 kOhm.
If ok, measure the 3 caps in the circuit, there may be one open or shorted
Keep my fingers crossed
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WB4YVO
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« Reply #80 on: June 21, 2018, 08:27:38 PM »

Ok,, The Osc is working..It runs 2.3 Mhz below the Carrier  so at 51 MHZ Osc runs at 48.7 Mhz  I can see on spectrum ANA the osc signal It varies along with frequency..

But hear is the catcher.. I used to measure the OSC frequency by putting a Antenna on my Freq counter.. And probing the chassis by the 6u8  IT would read the Frequency.. But now I get no reading on counter.. So I hooked up spectrum ANA with antenna and probed.. I can see signal not real low.. But maybe not as strong as it was.. Not sure because I didn't do it that way before so I have no reference to go by..

Skip..

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PA0NVD
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Nico and Chappie (Chappie is the dog...)


« Reply #81 on: June 21, 2018, 10:22:51 PM »

Hi Skip
That is the first oscillator. You need to measure the second oscillator of V9. That should run at 2,3-0.455=1.845 MHz or 2.3+0.455=2.755 MHz. You should measure at least a few volts at the cathode of V9, pin 2 using a scope. and a counter
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WB4YVO
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« Reply #82 on: June 21, 2018, 11:00:44 PM »

Ok  Understand  I put a scope on the cathode..  Got nothing..  I will try again tomorrow to make sure I am doing it right..

Thanks
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PA0NVD
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Nico and Chappie (Chappie is the dog...)


« Reply #83 on: June 22, 2018, 09:36:48 AM »

That makes sense, there is your problem. First try an other 6BE6
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WB4YVO
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« Reply #84 on: June 22, 2018, 09:37:26 PM »

Ok, Here is what I did..

Put scope on pin 2 of 6BE6 Got nothing .. Put in a new 6BE6  same .. So started to check a few components.  Noticed on pin 7 schematic says 68 Ohm.. Mine was 100 Ohm  But measured 130 Ohm.. So replaced it with a 68 Ohm

Next The cap on Pin 1 schematic said 47 UUF  I thought..  It had a 5 uuf..  so maybe schematic should have said 4.7 uuf ??  Took it out measured and put it back in..resoldered all connections on tube socket and coil L12..

Fired it up  It works again.. Checked pin 2 again and got a nice sign wave about 1 volt PK to PK.. Re aligned  and now getting approx 7 on scale for 50 uv input.. Spot function works again..

For how long it will work?? Who Knows..  Will try again in morning to see if still working..Still curious to what the pop was..

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PA0NVD
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Nico and Chappie (Chappie is the dog...)


« Reply #85 on: June 23, 2018, 10:08:24 AM »

Hi Skip
I really don't think that C89 should be 4.7 pF, it should be 47 pF, 4.7 pF may not give you a reliable oscillation or no at all.at this low frequency. That may the a part of the problem. Soldering quality is for sure an other problem. Please try to change to 47 pF and measure again the RF voltage at the cathode. I expect more than just 1 volt.
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WB4YVO
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« Reply #86 on: June 23, 2018, 02:55:29 PM »

Ok.. I will try that.. Have to see If I have a 47 PF Cap..

The one in there was tubular.. with colored bans.. looked almost like a resistor..

Colors Left to Right

Grn,Wht,Blk,Grn,Blk

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PA0NVD
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Nico and Chappie (Chappie is the dog...)


« Reply #87 on: June 23, 2018, 03:03:27 PM »

The value is not critical Skip, anything between 33 and 56 PF is ok.
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WB4YVO
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« Reply #88 on: June 23, 2018, 03:09:30 PM »

Ok will give it a try right now..

Skip
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PA0NVD
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Nico and Chappie (Chappie is the dog...)


« Reply #89 on: June 23, 2018, 03:45:04 PM »

When it works ok, you may have to adjust the oscillator coil L12. Put 2.3 MHz at point 2 of V8 via a few pF, just audible and adjust L12 for max signal.
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WB4YVO
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« Reply #90 on: June 23, 2018, 08:46:45 PM »

Yup did that.. Seems to be working so far.. Noticed that L12 peaked a little broader than before.. But signal strength is the same.
  I used a 33 Pf in parallel with the 5 pf  to give me 38 PF..

So far so good.. I said that before.. we will see when I try to put it in the case..

The Transmitter still puts out about 20 watts..

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PA0NVD
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Nico and Chappie (Chappie is the dog...)


« Reply #91 on: June 23, 2018, 10:17:41 PM »

Putting it into the case is when problems start, Murphy is still alive!!!. But no problem, as soon as you get it out of the case, it should work fine again to prevent that you find what was wrong... Smiley
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WB4YVO
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« Reply #92 on: June 24, 2018, 10:22:41 PM »

Ok, Stopped working again.. Still have a intermittent connection somewhere in the 2.3 Mhz IF's  If I tap the IF case it makes all kind of noise and squeals ETC..   I think I will take them out and inspect the insides.. Maybe the Caps are bad or intermittent inside cans..

Oh goody did not  even have a chance to get it into case before it stopped working this time..

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PA0NVD
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Nico and Chappie (Chappie is the dog...)


« Reply #93 on: June 24, 2018, 10:55:33 PM »

you are lucky  Huh If you should have put it into the case, you should have to take it out again.....
Don't know what they used as a flux during soldering, but it was really bad Skip. Did't hear so many problems wit bad soldering s. May be an other one?
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WB4YVO
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« Reply #94 on: June 24, 2018, 11:29:35 PM »

Yup, Could be.. Well I am pretty sure its around the 2.3 Mhz IF cans.. T4 and T5..

So I will remove the cans.. I did that before and could not find anything that looked bad.. I will have to do a better inspection this time..

Skip..
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WB4YVO
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« Reply #95 on: June 25, 2018, 06:44:54 PM »

Ok, Removed the coils  All looks good could not find any problems.. However I was tuning one of the slugs and it broke. I cannot seem to get it out .. Anyone know of a way to get this out without destroying the coil?

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PA0NVD
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Nico and Chappie (Chappie is the dog...)


« Reply #96 on: June 25, 2018, 07:17:22 PM »

That is the nightmare of the restaurateur...I went through that several times.
If it is mounted with wax (many are), heating will sometime help. When I can't get one out, I break pieces off and put a second slug on top to compensate for the loss of material.
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WB4YVO
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« Reply #97 on: July 01, 2018, 07:33:25 PM »

OK Finally was able to get back to this.. Reinstalled the 2.3 Mhz IF Coils.. Could not find anything wrong with them..

Realigned radio.. Radio now works as before.. I did fix the S-Meter circuit that I had not gotten to before ..

Now a 50 uv signal =9 on meter..  Reinstalled the front panel.. Radio is still working..

Now to put it in case.. going out to garage to do that now..Wish me luck..

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WB4YVO
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« Reply #98 on: July 01, 2018, 08:17:52 PM »

Ok back in case.. Still working  Did a drop test a couple of times  No problems.. TX still at 20 watts or so.. Did notice the in VFO mode it puts out about 2-3 watts less power than in Xtal mode..

No big deal..

So on to the next..

Thanks to all for helping me get this up and running.. Especially Nico..

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KD1SH
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« Reply #99 on: July 01, 2018, 08:53:55 PM »

   Now that's interesting; mine puts out a few watts more in VFO mode than in crystal.  Go figure.  What's more, when in crystal mode my power output will do a slow drift, maybe three or four watts or so, slowly falling off and then returning just as slowly.  I haven't tried changing out the 6AU6 yet, but I think I will.  Power output drifts very slightly in VFO mode.  I'm getting 30+ watts from mine most of the time.
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