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Gonset G-50




 
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WB4YVO
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« Reply #25 on: June 03, 2018, 01:05:00 AM »

Well, scratching pins and lubricating didn't do anything.. Probably did a little worse.. I cannot find a spot that will work perfectly now  ..I can get somewhat of a signal but very scratchy.. 

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


« Reply #26 on: June 03, 2018, 10:08:59 AM »

That's weird, so resolder the sockets again may help. When moving the tube does change things, it must be a bad contact in that area. I don't know what kind of resistors the set uses, I had once a carbon composite resistor that had a bad contact inside the body. Took me quite a while to find.
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WB4YVO
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« Reply #27 on: June 03, 2018, 09:09:51 PM »

Ok re soldered connections..That seemed to help alot.. Went thru alignment procedure with no problems.. Can receive signals from SG with good tone..

So that is all good.. However Sensitivity is extremely poor.. Says a 50 UV signal should read S9 .. I can barely hear a 50 uv signal. If at all .. S meter doesnt seem  to work right either.. Will not zero.. reading at about S2.5  No signal..

Skip

PS so making progress .. one step at a time..
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PA0NVD
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« Reply #28 on: June 03, 2018, 10:08:26 PM »

Hi Skip
If you hear noise, I suppose the problem is in the RF amp or first mixer. Noise means sensitivity (in general)
Due to the experience with the solder problems of the other tube, start with re-flowing the solder at the RF tube socket.
If that doesn't solve the problem, try to measure the following:
Try fist to inject 2.3 MHz via a small cap (approx 10 pF) to the grid of the first mixer, but you have to de-solder C47, the 47 pF
Align the IF for max signal.
Than change the frequency to e.g. 51 MHz, tune the receiver and define the sensitivity again. Shouldn't be very much different.
Than re- solder C47 and change the signal injector cap to  1 pF. The sensitivity should not change much,  (re-allign L7, the anode coil of the RF amp for max signal).
Than change the signal via the 1pF to the grid of the RF amp, re-allign L7 and T9 and define the sensitivity again. Should be at least   3 - 4 times more sensitive.
I am curious about these figures.
They are NON-impedance matched figures, so after impedance matching (going to a normal 50 Ohm input) the last measurement should improve at least 10 dB
Regards
Nico
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WB4YVO
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« Reply #29 on: June 04, 2018, 03:27:18 PM »

Well here we go.. Followed your instructions.. When all was said and done  Had approx 40 db difference..

step  1       Very  little difference
Step 2         little bit better may 1 DB difference

Step 3.       Approx 40 db difference  Now could hear 50 Uv signal at around S5..  Could actually hear a 1uv signal but very weak..

 So big improvement..

So is the alignment procedure from factory wrong??

Ok s meter is still not zeroing.. in fact when tuning from one end of band to other the s meter moves probably moves 2 s units.  Zero pot is at the stop..

Skip 
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PA0NVD
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« Reply #30 on: June 04, 2018, 05:23:23 PM »

Hi Skip
Good to hear the improvement. I don't think that the factory adjustments are wrong, but you have to take into account that value's of caps and resistors may have changed. In addition, there is interaction, especially with band filters, so many procedures have to be repeated. A problem are the magnetically or capacitive coupled band filter. When the Q x k, is less than one, you can peak at the signal. But when critically coupled (ideal) this becomes difficult and when over coupled, there are two peaks. So bandfilters should ideally be aligned with a spectrum analyser and tracking generator or with a wobbling system. But to keep it simple, a repeated peaking at a weak signal in general will do.
So, in order to avoid drift during tuning, enter a small, just audible signal at 2.3 MHz at the grid of the first mixer pin 2 of V8 via a few pF. You don't have to un-solder anything. Now peak both IF strips repeatedly. Keep the signal just audible or measure the detected signal with a voltmeter or scope and just adjust for max signal.
Next is the adjustment of the oscillator coil T10 and the trimmer C52
--Tune to the lowest frequency of the scale and adjust the core in T10 for reception.
--Tune to the highest point and see if the scale is correct. If the receiver receives higher frequencies that the scale suggest, tune C52 for a larger cap until you receive the signal that the scale indicates and OVERSHOOT that alignment just a little
When you receive a lower frequency than the scale indicates, tune C52 for a smaller value and overshoot the adjustment just a little
--Return to the lowest frequency of the scale and readjust L10 again for reception.
This procedure has to be repeated several times until the scale indicates the correct reception frequency. During the last adjustments you should not overshoot the adjustment anymore.
If all ok, the alignment should be acceptable over the whole scale.
Now you can adjust the two RF coils T9 and L7 for max signal in the middle of the band and you should be ready.
When you tune across the band with a dummy attached, the noise  and sensitivity should not vary more than half an S point or less.
When not, tell me and I try to make a procedure to correct the problem.
Success Skip
Nico
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PA0NVD
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Nico and Chappie (Chappie is the dog...)


« Reply #31 on: June 04, 2018, 05:38:20 PM »

My HQ170 has a similar issue. It motorboats when the band width is in the 2 KHZ position but is OK otherwise.

Any ideas?

Thanks, Rich

Hi Rich
Did the above conversation solve your problem with the HQ170 ?
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WB4YVO
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« Reply #32 on: June 04, 2018, 08:19:35 PM »

Ok followed your procedure.. All went well.. Looks like set is more sensitive at low end of band since AM activity is at 50.4 should be good to go..I would like to get S-meter to zero. and get it adjusted for 50uv=S9..

What I have read was the voltage divider circuit is R40/R41  Pot (5K) and R57  4.7K 1W..

After zero if reading does not equal S9 then either increase or decrease R44 ( 33K) For S9 reading..

Skip

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PA0NVD
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« Reply #33 on: June 04, 2018, 11:40:06 PM »

That's indeed so Skip, the pot R20 (5k) is for zeroing the meter and R44 (33k) is the sensitivity
The meter depends on the anode current of the 6BH6 affected by the AVC. So the complete alignment, the amplification and the quality of the 6BH6 all affects the meter reading.
So when you change a tube, the meter reading may be off again
Please let me know when you had the first QSO with the set!!  I did sent an Email upwards to ask for good conditions at 6  Grin
Nico
nicomaria1945@gmail.com
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WB4YVO
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« Reply #34 on: June 05, 2018, 07:57:10 PM »

Well, On to the Transmitter.. I guess I am still not done yet.. The spot function works well. However when trying to load I get NO Plate current at all..So of course NO dip..

Skip...

l
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PA0NVD
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« Reply #35 on: June 05, 2018, 10:30:02 PM »

Seems that the set keeps you out of the bar Skip So this set will keep your wife happy  Wink
I suppose that the 6146 glows normal The tests below suppose a working 6146
When the spot function works, that means that the oscillator runs fine. If the driver Q2 works, you should get grid current. except if there is no cathode connection or if the 6146 gridleak R10 is open. Drive to a grid with an open grid leak will result in a tube cut-off and hardly any anode current.
Measure first the voltage at the anode during transmission, the choke may be bad.
If there is no grid current, measure the value of R10, 15 k, 1 Watt grid leak for the 6146
If there is grid current, than:
In order to exclude a meter circuit fault, please measure the voltage at the cathode of the 6146 during transmission. Work fast and keep an eye on the 6146 that it does not get red hot or so. The voltage should be something like half a volt.
If no voltage, measure the voltage of G2, pin 3, should be HV. If no voltage, measure at the other side of R15, he G2 resistor of 18k, 2 Watt. That resistor may be toasted. If so, please change C23 first, that may be the cause of an R15 failure.
Hear the results
Regards
Nico
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WB4YVO
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« Reply #36 on: June 06, 2018, 02:14:29 PM »

Ok, Prelimary readings.. Resistance

R15  Should be 18K  Reads 19K
R10  Shoulod be 15K Reads 17K

R11 Should be 470 Ohms  reads 500 Ohms
R12 Should be 1.5K Reads 1.665K

But here is the kicker.  From Pin 1 to Pin 3 there is a 6.8 Meg resistor  Not on schematic.. Reads 7.8 Meg

Nothing shorted to Ground.. Did not measure all the .01 or .02 Uf caps yet..

Will power up and measure Voltages..

Oh it has a 6146 tube in  Not a A or B version.. If that makes a difference..

Skip..

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PA0NVD
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« Reply #37 on: June 06, 2018, 03:04:43 PM »

There is little difference between 6146, A or B. The B version is especially made for VHF and may be preferred. But I doubt if you notice a difference
I don't think that you have to replace a resistor, all sufficiently close. That 6.8 M is not that strange, goes from G2 to the cathode. It seems to me that the open cathode at reception may have caused problems and they pull-up the cathode softly to keep the tube completely cut-off during reception. Not uncommon practice, a floating electrode is not a good defined thing. I should keep it like it is.
So seems that there may be no HV, bad anode choke, or one of the decoupling caps is bad. Other possibility is that the relay contact in the cathode S1 doesn't make contact. If so, you will measure quite a high positive voltage at the cathode at transmission, around a +50 V or more
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WB4YVO
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« Reply #38 on: June 06, 2018, 03:59:39 PM »

Ok.. Here is what I measure..

6146  B+  RX  230 Volts
6146  B+  TX  328 Volts

Cathode  RX  197 Volts
Cathode TX   .4 Volts

Also measured pin 5 of 6146 with scope  Had signal in TX..

But still no grid or plate current indicated ..

Skip
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w4bfs
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« Reply #39 on: June 06, 2018, 04:15:17 PM »

meter switching and current shunts
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« Reply #40 on: June 06, 2018, 04:47:34 PM »

Quote
No need to feel stupid,  at least you didn't wire them in backwards.  In fact, folks who have wired their electrolytic s in backwards have been banned from the Forum.

That's why people should always use non polarized caps! Be very careful less you be Shanghaied to QRZ.COM..........  Oh NO the shame Tongue Tongue Tongue
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PA0NVD
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« Reply #41 on: June 06, 2018, 04:58:43 PM »

Indeed what W4BFS said, meter circuit. When you measure 0,4 V at the cathode, the 6146 pulls 40 mA
So I suppose that the ground connection of the switching circuit is open at S5 because you don't measure Ia nor Ig or mod. If only R16 of 2k2 was bad, you should measure Ig
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WB4YVO
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« Reply #42 on: June 06, 2018, 08:52:25 PM »

Well, Checked out meter circuits all is good. ground connection is good ..I guess I will try a alignment.. Maybe its so out of wack that there is not enough drive to do anything..

Cannot think of anything else to do at this point..

Skip
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PA0NVD
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« Reply #43 on: June 06, 2018, 10:03:24 PM »

Must be in the meter circuit Skip. When there is 0.4 Volts over the cathode resistor R14, there is running 40 mA. With the meter series resistance of 2.2 k, the meter should show 0,4/2.2=0.18 mA (approx. ) that is almost 20% FS
Does the relay  S1 below the meter make good contact in Xmt? Does the meter show when in MOD and you modulate?
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PA0NVD
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« Reply #44 on: June 06, 2018, 10:12:59 PM »

You can put 2.2Volts from a low voltage power supply at the left side of the 2k2 series resistor R16. Than there is running 220 mA through R14, the cathode resistor, transmitter off, not powered at all. In Ia the meter should show FS. If not, go fault isolating from there.
For Ig, you can put 1,5 VDC NEGATIVE over the 470 Ohm resistor R11 at the connection point of R10, R11 and R12
In the switch position IG the meter should show FS
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WB4YVO
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« Reply #45 on: June 06, 2018, 10:47:53 PM »

I have not tried to  modulate.. I will have to rig up a mic to try that.. But will try to see if meter circuit is good by doing the voltage trick..

Thanks

Skip
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PA0NVD
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« Reply #46 on: June 06, 2018, 11:59:17 PM »

The Xmt relay should be energized in order to switch over the contacts below the meter. Or you can push it over by hand
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WB4YVO
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« Reply #47 on: June 07, 2018, 11:15:52 AM »

OK.. here are measurements with power supply..

Grid meter  -.66 volts  Reading 3.5 on scale
               -1.772 volts  Reading 9

Plate meter..   .646 Volts 2.5 on scale
                    2.5 volts    9

Ok so meter circuits working..

There is no relay.. All connections are made thru a  12 pole 2 position 3 section switch.. you manually go from RX to TX via the switch  So to take readings switch had to be in TX position..

I  think I need to work on the meter Zero.  When in RX the meter reads about a 3.. I cannot zero it using the Zero pot..  Probably has nothing to do with TX  .. I will see what readings I get on Grid position and plate when powered up..



Skip...   
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PA0NVD
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« Reply #48 on: June 07, 2018, 04:41:43 PM »

Hi Skip
Can you replace the meter temporarily with an external meter of 1 mA to exclude meter faults? It seem that the meter reads quite low, perhaps the zero is completely off..
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WB4YVO
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« Reply #49 on: June 07, 2018, 06:22:57 PM »

OK,, All is working fine now.. This is what I did..

UPDATE::::I was going to follow the alignment procedure I have for TX  So firts thing it said was to tack solder a 680 Ohm resistor across the coil L4.. So I did that..  Then it said  to hook up a VTVM from Junction of R10/R11  and adjust L5 for MAX.. So when I went into TX I all of sudden had Plate current about and 8 on meter..But no indication on VTVM.. So I decided to disconnect resistor.. Then went to TX and still had Plate current  Was able to dip and peak controls to get power out put on my Wattmeter..  I didn't have the right slug for bird meter so I am not sure what power is.. But its there..

So maybe a bad solder connection???

I will hook up the right meter and try again in a few to see if its still working..

Skip...
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