The AM Forum

Greetings!

I will try to get all pertinent info into this note hoping that someone can assist me. I have a DX-60A that I completely restored by replacing nearly all of the caps except for C3 (100pf on V1), C21 (68pf on Band Switch) and C19 (.001mf on RF Choke) and C42/C43 (.005mf on AC Line). I replaced all resistors except for R28 (10k 2w on Function Switch) I forgot to order that one and it measures 13k ohms. All electrolytic caps have been replaced, as well as the diodes with 1N4007s.

The only mod I did was a snubber found at VE6KQ.com, see attached images. The problem pre-existed this mod!

1- Using a Heathkit HG10 VFO, I get ZERO, nothing on 10 meters. No meter indication for Grid or Plate voltage at all. All other bands load fine, save 15 which loads poorly.

2- Using 80m as my example, the Plate voltage will never load over 98ma.

3- The radio puts out about 10w on AM.

My  Bias voltage is -80 in standby mode, here are the readings with a crystal and VFO with Key Down. Reference is what is published on the schematic.

VFO V1 Pin 6 = 259v        XTAL V1 Pin 6 = 300v           REF V1 Pin 6 = 310v
VFO V1 Pin 8 = 127v        XTAL V1 Pin 8 = 186v           REF V1 Pin 8 = 215v
VFO V1 Pin 9 = -0.46v      XTAL V1 Pin 9 = -24v           REF V1 Pin 9 = -25v

VFO V2 Pin 6 = 276v        XTAL V2 Pin 6 = 309v           REF V2 Pin 6 = 340v
VFO V2 Pin 8 = 137v        XTAL V2 Pin 8 = 9.78v          REF V2 Pin 8 = 12v
VFO V2 Pin 9 = -3.3v       XTAL V2 Pin 9 = -33v           REF V2 Pin 9 = -115v

VFO V3 Pin 1 = 0.5v        XTAL V3 Pin 1 = .5v              REF V3 Pin 1 = 1.2v
VFO V3 Pin 3 = 84v         XTAL V3 Pin 3 = 78.8v           REF V3 Pin 3 = 65v
VFO V3 Pin 5 = -28v        XTAL V3 Pin 5 = -27.7v         REF V3 Pin 5 = -38v

VFO V4 Pin 1 = 710v        XTAL V4 Pin 1 = 714v           REF V4 Pin 1 = 720v
VFO V4 Pin 2 = 50v         XTAL V4 Pin 2 = 49v             REF V4 Pin 2 = 25v
VFO V4 Pin 6 = 50v         XTAL V4 Pin 6 = 49v             REF V4 Pin 6 = 25v
VFO V4 Pin 7 = -2.2v       XTAL V4 Pin 7 = -2.2v          REF V4 Pin 7 = -1.0v

VFO V5 Pin 1 = 122v        XTAL V5 Pin 1 = 133v           REF V5 Pin 1 = 135v
VFO V5 Pin 2 = 0.1mv      XTAL V5 Pin 2 = 0.2mv          REF V5 Pin 2 = 0v
VFO V5 Pin 3 = 1.3v        XTAL V5 Pin 3 = 1.4v            REF V5 Pin 3 = 1.3v
VFO V5 Pin 6 = 80v         XTAL V5 Pin 6 = 82v             REF V5 Pin 6 = 80v
VFO V5 Pin 7 = -0.7v       XTAL V5 Pin 7 = -0.7v          REF V5 Pin 7 = -0.7v

I have attached an image of the voltage readings in case the text format gets all SNAFU.

Can anyone help me address these discrepancies?
Is the radio OKAY to use in this state?

Tnx and 73

Rik
w2rik

What kind of probe did you use to determine the bias on Pin 5 V3 and the voltages of the RF amps during AM keydown?

Were all of these readings on 10 meters?

My first inclination is to check L1 for proper adjustment and connections, then make sure C2 is 100 pF in value.

Also, make sure R13 = 8.2 ohms. If it is bad and you don't have an 8.2 ohms, use a 10 ohm 1W and a 47 ohm 1/2 W in parallel.

Phil - AC0OB

I just used a multi-meter. I took my readings on 80 where I loaded up. C2 is listed as .005, should I change it to a 100pf? R13 is fine.

I did work 80m tonight and was told I had a good signal and audio. Then I tried 40m. The rig loaded up but it only put out 1 or 2 watts?!

I will double check L1 tomorrow. Now I don't have a 40m crystal as the manual suggests on pg 36 (see attachment). Will the VFO give me the same result? Maybe L1 being out of whack is why 40m didn't work. 

 Tnx Phil!

My bad, C3 should be the 100 pF cap. C2 is 0.005 uF. The mica C3 has been problematic on some units.

Without a special probe, RF will get into your multimeter and give you false readings. The input capacitance of most multimeters will reduce RF on the plate or grid pins.

Voltage readings should be taken at the bottom of any inductor where there is usually a 0.005 uF RF shunt capacitor to ground.

Another thing to check are the bandswitches and their contacts with a bright light and a magnifying glass. Make sure C21 is not getting switched in on any band but 80m and that the other L2 AND L3 coil taps are getting shorted as you go up in frequency.

Phil - AC0OB

I will check this out tomorrow and get back to you. Tnx!

Is the VFO up to the task?

Yes, the VFO is fine.

Maybe I need to be schooled on the DX-60 operation?

I adjusted the 40m drive coil and that seemed to make all the bands load up. Here is were I may need an education... When I load up using a DUMMY LOAD, I will obtain the 150 ma in the CW position. Once I switch over to my antenna, I get about 98 ma. Looking at the output, the radio is consistent with about 10 w on AM and about 50 w on CW.

OK, so my QTH is NY about 35 miles from NYC as a crow flies. I was in a QSO with one station working his New Hampshire station remotely and another in S. Carolina. They both said I had a great signal esp. for a DX-60.

Then as I was talking, a fuse blue. I replaced it and the radio wouldn't load up. I put it on the bench and tried to load it and when I dipped the plate, the fuse (3AG) blew again.

What's going on??????????????  ???

Is this pointing back to the bias issue I thought I had?

What size fuse are you using??

You never mentioned the grid drive or the Final grid current. Final grid current should be about 2.5-3 mA.

Pages 33-35 of the manual gives you the tune up procedure.

Phil - AC0OB

I follow the load up as directed in the manual and set it to 2.5 ma.

The fuse is a 3 amp, 250 volt.

Does the manual show what size fuse should be used.  Reason I ask is you referred to the fuse as 3AG.  3AG is the type of fuse (same as type AGC).  3 amp is probably about the lowest value to use for that xmtr.  You may need a slo blo fuse or a higher current fuse.

Fred

That's a good point Fred. The original fuse was a neon bulb that blew out years ago. At that time I drilled a hole in the chassis and installed a fuse holder. When I google searched at that time, the most popular answer was just a 3 amp and no mention of a slo-blow.

Maybe Phil can comment on what he uses.

But my concern is now the fuse is blowing out on load up, it didn't do that before and as stated, I was in a QSO when it happens tonight.

The attached image is the driver plate coil at lug 5. Did the contact break off the rivet? I took this pic earlier today before I went on the air.

The last time I worked on a Heath DX xmtr was over 50 years ago so I don't remember.  3 amp seems a little marginal for a xmtr, especially with today's higher line voltages.  The 3 amp fuse may be running on the edge and with normal operating surges the quick acting fuse may be just blowing.

Never saw a neon light being used for a fuse so I'm not sure what that's all about.  Most of those xmtrs used a special AC plug that had two fuses in the plug.  Someone probably removed that AC plug or replaced the whole line cord.  That's why the rig had no AC fuse holder.

Fred

Not uncommon for a rotary switch to have unused dummy contacts.  The dummy contact is just there to be used as a circuit tie point.

 Maybe it's not a neon bulb but it sure looked like one  ;D

See attached.

OK,  I have seen that type circuit breaker.  They do look like neon bulbs.  They were automatically resetting.  You did the right thing by replacing it with a real fuse.

Fred

The schematic section you posted earlier is for a DX-60B. Are you using a DX-60 or a DX-60B because the voltages on the various tubes are somewhat different? There are also some circuit differences in the power supply area.
The DX-60 specification is 90 watts input power on CW. If you can achieve 70% efficiency that's roughly 63 watts output on CW given everything is working the way if should. On 10 and 15 meters, output would be lower. Switching to AM, the carrier output power will be even lower since the screen grid of the 6146 now is only at 65 volts rather then 150 volts (DX-60B schematic says 180 volts) for CW. When you modulate the rig, the screen grid voltage and plate current will "undulate" upward as you talk. Also, the parts list for the DX-60 and DX-60B show two different part numbers for the power transformer but no other info relative to ratings.

Interesting thread & photos.  Not to say that the fuse rating shouldn't be higher, but if it the transmitter was working okay before, I would suspect that the fuse rating is not the problem, but rather an indication of a failure elsewhere.  I'm wondering if any components in the PS have failed or are deteriorating.

Here's the thing... all components, i.e. resistors, caps, diodes have been replaced with modern parts except for the few that I mentioned in my opening comments.

Can someone tell me where to start looking because I can load the 2.5 ma grid current but as soon as I try to load the plate, *POP*, the fuse blows.

Another thing..., as I was checking voltages in the TUNE position with the 2.5 ma loaded but no Plate, maybe after about 20 -30 seconds the fuse blew.

No smoke or sparks and only two resistors were hot to touch, R4 (15k, 2w on V1 pin 8 ) and R1 (47k, 1/2w on pin 9). Both read OK.

Now this is a DX-60A but I used the manual for the DX-60B because the A is unavailable. I did install the power supply caps according to the B version. See attached.

The power supply wiring and components differ between the DX-60A and DX-60B. Transformers are also different. The DX-60A using three electrolytic caps in the HV supply; DX-60B uses four. R4 should be warm (relative hot); it's a screen resistor. R1 shouldn't be hot unless it's passing a lot of current. You might try reversing the two 6CL6's and see if the "hotness" changes with those two resistors. You might also check to make sure there's nothing shorted in the crystal/VFO switch and wiring. Is the 6146 good?

First, Tnx to everyone who replied. I really appreciate the feedback.

Do you think there is a problem created by adding the extra cap? The 6146 is good, it tests very well on my tube tester but I realize that's not under load. I will try swapping the 6CL6.

I have visually looked at the crystal/VFO but can't seem to see anything. Do you have any tips for that?

Interesting, after switching the two 6CL6 tubes, R1 didn't get hot like before. However, the fuse did pop again while in tune mode after about 20 seconds.

Now take all the tubes out of their sockets except for the 1st 6CL6, power it up; fuse OK yes/no
If OK, put 2nd 6CL6 in socket, power it up; fuse OK yes/no
If OK put 6146 in socket, power it up; fuse OK yes/no
If OK put 6DE7 in socket, power it up; fuse OK yes/no
Try tune, cw, am positions each time to see if the fuse goes.

Very good!

I put in 6DE7 and when I tried to load the fuse blew. If you noticed, on my opening note I was getting 50v on pins 2 and 6.

Next step?

I just tried to read the voltages on V4 and as soon as my probe touched pin 2, the fuse blew.

Does this xmtr have caps on the incoming AC line??  If it does and they are original, remove them.  You don't need AC line caps.

Your DC probe should not be causing fuses to blow unless you shorted something when you use it.

If you'd like to save some fuses, build one of these. Comes in handy for a variety of things.

It's a fuse saver.  You'll need to select an incandescent bulb that won't draw more than an amp or more over the rated fuse in the rig. 

If all is good the bulb should be dim or dimmer than full voltage across the bulb when the rig is operating as it should.  If there's a short in the rig or abnormal current draw, the bulb will glow full brightness or very close to full brightness.  Select the appropriate wattage bulb.  I have a variety of bulbs on hand from 25w to 200w I use for testing.

It's a cheap and dirty variac and fuse saver.

Tnx Bob!

Fred, I will remove those caps, Tnx.

Ok, so I put the 6DE7 in my tube-tester and it is completely DEAD! I am hesitant to put another tube in there for fear of blowing it until I can figure out why the voltage was off.

Just FYI.

Harbor freight fuses are garbage.   I was working on an amp that had blown a fuse I didn't have,  and harbor freight is the closest place with an asst. 

Got home,  two 20 amp fuses blew in a row.   Upon inspecting the HF fuses left,  one end was able to be pulled off the glass.   Caused a hot spot on the fuse there because they rely on friction to make electrical contact.

The 20 amp fuses blow apart at 10 to 12 amps.

Just in case you made the same mistake on a purchase of them as I did.....

--Shane
KD6VXI

I didn't know that Harbor Freight sold fuses. These are probably the same cheap Chinese crap, although packaged by Radio Shack.

I would check the two caps and the two resistors coming off of Pin 9 and the resistor between Pin 1 and Pins 2 & 6 for starters. The 6DE7 is used as the modulator, so with it out, you should be to play and check operating voltages/characteristics on various bands with the transmitter in the CW mode.

Pete,

Both pins 8 and 9 on V4 are grounded, it doesn't matter which leg of C35 or R26, they are both grounded.

Looks like C35 shorted. I will put the original cap back in and see what happens.

Well, I thought that I was on to something.  I'm surprised that the cap rated for 630v blew out.

The same problem is there, when I load up, the fuse blows.

Maybe the coupling cap from the plate of the final and the Pi network is shorting under the load.  Did you replace that cap.

What do you mean, "dead?"

No filament or shorted elements?

This tube is a "dissimilar" dual triode with each separate triode having different gains and power handling capabilities.

Phil - AC0OB

The filaments lit up but no movement on the meter scale.

You most likely touched pin 2 and 1. Pin 1 has 700 volts on it.

Do that and the Final's screen voltage goes very high making the Final conduct a lot of current probably contributing to blown fuses.

C34 (DX-60 schematic) or C35 (DX-60B schematic) are 100 pF 500V units.

Which schematic are you looking at?

No, I didn't replace C18.

Does anyone have the DX-60A manual in PDF?

This is what I used to check my Ameritron HV transformer when it was blowing fuses.  Not as fancy as yours but it worked.  Worked pretty slick.  As soon as an internal arc occurred, the bulb (a 60 watter) would flash brighter thus limiting the primary current.

Al

Folks,

Here is an update. I returned to PS section back to its original configuration with three capacitors, not four as I previously had.

I removed all the tubes and added them one at a time. The radio tripped when I switched to CW and tried to load up with only V1, V2 and V3 installed.

The readings using an 80m crystal on V1 looked good, however V2 not so much.

XTAL V2 Pin 6 = 322v           REF V2 Pin 6 = 340v
XTAL V2 Pin 8 = 6.5v           REF V2 Pin 8 = 12v
XTAL V2 Pin 9 = -37v           REF V2 Pin 9 = -115v

The 1Mh choke on Pin 9 is reading 30 ohms... Isn't that extremely high?

The choke reading is normal. You need to read the DC voltages at the bottom of V2's grid choke and the bottom of R8.

What was the voltage at V4 pin 3 screen grid when it blew another fuse?

Check your 6146 again and make sure you didn't blow it when you shorted pins on V4.



Both versions of the DX-60 series have four - 40 uF electrolytics in the power supply.

Have you replaced C18/C21?

Here is the DX-60B schematic.


Phil - AC0OB




I have the DX-60 Manual as well so PM me if you need it. Can't upload it here.

I mH RFC could read 30 ohms.  What are tubes V1 V2 V3  I don't have a drawing.  What final plate current are you seeing.   Before you switch to transmit you need to tune the driver stages to be sure you have enough drive to the final stage.  A 6146 should have 2.5 to 3 ma of drive.  Once you're sure you have drive, switch the meter to read plate current.  Switch into transmit with key UP.  Nothing should happen.  No fuses should blow.  Key down, quickly look at the plate current and dip the final.  If the plate current is not too high to begin with (say 150 ma)  no fuses should blow.  Dip the final, load up to about 110 ma.  No fuses should blow.

Of course use a dummy load or an antenna for the load.  If you can't get past these basic steps, which apply to any xmtr,  you need to start back at the beginning and check all wiring and components.

OTH if you can get past these steps and you have power output (say 50 watts) and as you may be transmitting some CW, the fuse blows,  you need a little bit heavier fuse (say 4 amps).  IMO I think a 3amp fuse is a little light for that xmtr.

Fred

Yes, The DX-60 and DX-60B use 4 caps. I have the DX-60A and attached the schematic. The difference between the A & B is in the extra cap and a 7w resistor. Also R36 and R37 are wired differently.

I didn't replace C18 or C21. I couldn't find C21 in it's value and will this work for C18? (See attached).

I tested the tube and it was OKAY, same reading as last time.

That cap you pictured will not work for C-18,  You need a door knob cap or a ceramic cap and the voltage rating should be at least 5KV.

Fred

Okay, in your original post you said DX-60 so that's why some of us are confused.

For C18 it would be preferable to use a 0.001 uF (1,000 pF) 2kV ceramic.

Phil - AC0OB

V1 6CL6 Crystal Oscillator
V2 6CL6 Driver
V3 6146 Final Amp
V4 6DE7 Modulator
V5 12AX7 Speech Amplifier

I was on the radio in a QSO and the fuse blew mid-way. If you look back at my first post I did before the QSO, I was looking for assistance with wacky voltages. The fuse blowing came later and that's where I am now.

The 6146 does have 2.5 ma of drive and it's when I dip the plate and increase the Final Tuning in CW mode (per manual), the fuse blows.

Oops! I corrected the Subject and text. Tnx Phil.

Those yellow caps, like what you pictured, should not be used anywhere in the RF sections of the xmtr  You need ceramic disc caps in the RF sections.

C-21 in another cap that should have high voltage rating,  it is part of the plate tuning capacitor on the lower bands.

Understood on the ceramic caps. Isn't C18 the Domino Mica cap? Do you think that needs to be changed?

Those large postage stamp micas can be problematic especially the red ones.  Problem is finding the right cap to replace it with.

Searched on line for a manual for a DX-60.  Found one,  it showed a 3amp fuse in the parts list.  Wonder why Heath went to the circuit breaker in your rig.  Could the circuit breaker been rated a little higher than 3 amps?  Circuit breakers are slow to react to an overload.  At the least you need to try a 3amp slo blo fuse or try a slightly higher value fuse.

If you have a Variac, try running the rig on slightly lower line voltage (say 115 vac).  Right now, with everything you've done and posted, we don't know if there is something that is breaking down under load or the fuses you're using are not right.

If you had an accurate AC amp meter you could put that in line and measure the AC current.  Easy for me to say, i have a dozen lab type AC amp meters than can measure from millamps to 200 amps.

No amp meter,  if you have a 1ohm resistor at about 10-20watts,  put it in line with the power line cord (put it in line with the white neutral wire).  Use a DVM and measure the voltage drop across the 1ohm resistor.  1 volt ac equals 1 amp.  Of course you would use an external set up that you would plug in the rigs line cord to.

Again, at this stuff is easy for me,  I have a 300watt 1ohm resistor already made up for this purpose.

Fred

 

I do have a variac and set it at 115 v. I also have a meter called a Kill-a-Watt (see image) on it and here are the readings:

Standby - .28 Amps
Tuning up, Key Down, CW - 1.19 Amps, then the fuse* blew.

*I put the stock circuit breaker back in line to save on fuses.

OK great,  does that Kill-a-Watt meter read amps or just wattage or both??  Two amps shouldn't be blowing fuses.  So, there must be something breaking down under load.  Not easy to find these type problem.

Fred

It will display Volts, Amps, Watts, Hz, VA.

Is it possible that the .005 caps on the 6146 are failing?

I've been working with electronics over 55 yrs,  I don't think I've ever seen more than 5 or 6 bad ceramic caps.  If the .005ufd caps are ceramics it's unlikely they're bad.

Looked at the schematic,  C-18 would be the more likely cap to be bad.

What are you using for a dummy load or antenna??  Reason I ask is that if C-18 was maybe breaking down inside your HV will short through the pie network through the dummy load to ground.  That will blow the fuse every time.  If your antenna is a dipole,  a short circuit through the antenna wouldn't occur.

I see that xmtr has some added low pass filtering after the pie network,  have to take a closer look at that for any possible problems.

Fred

When the issue of the fuse blowing first occurred, I was in QSO and using an Alpha-Delta LB-DX+. For a dummy, I have been using a light bulb and it's the same one that I have been using all along.

I can't seem to find a .001 in 4Kv.

The only change I made in the filter cage was changing the RCA phono plug to an SO-239, see attached.

A 3amp fuse popping at 1.2amps????   Sure it's a 3amp fuse?

Yes, but I reinstalled the stock circuit breaker and when I say the fuse blew, it's the circuit breaker that resets itself in about 7 seconds.

Not sure what the Alpha Delta antenna is but it may be a DC grounded antenna.  You can put an ohmmeter on the coax end to see if it is.

The plate coupling cap (C-18) can be a pain to find a replacement.  In my HB 6146 rig I used an old TV door knob cap.  Most are 500pfd at 20KV,  works FB.  In my HB 813 rig I used two 680pfd at 18KV, both door knob type caps.

Here's a test you can do.  Remove the 6146,  power up the rig,  carefully measure the HV at the top of the final plate RFC.  You should see the 5-600 volts from the PS.  Now check for any leaking DC voltage on the other side of the plate coupling cap (C-18),  the end connected to the plate tuning cap.  If you are seeing any amount of DC voltage on that end, for sure the cap is NG.  By this time, 50 plus years,  most of those type micas are bad.  I have boxes of them but wouldn't think of using them.

Make sure to remove the 6146 from the socket.  Reason is the screen will draw heavy current with the plate voltage absent, which can quickly damage the tube.

Also disconnect any antenna or dummy load while doing the test.

Fred.

Fred, the Alpha Delta antenna is good from 160-10m (see image).

I did the test and get 720 v on top of the RFC and an up/down from 0 to .600 mv on the other side of the cap.

OK on the antenna.  Only a few millivolts is better than I thought you would see.  Doesn't seem like it's leaky, so, less likely it might be the cause of the fuse blowing.  For now leave it in there and look elsewhere for the problem.  I'm not sure where to look next.

Have you tried any transmitting with the circuit breaker in line.  Might be the next step,  see what happens.  The circuit breaker is slower to react to an overload.  While transmitting keep an eye the plate current.  You may see it shoot up or even pin the meter before the circuit breaker reacts.  You need something to point you in the right direction.  You may even keep an eye on the Kill a Watt meter using the current mode.

It would take a heavy load on the HV line or the low voltage (300V) line to blow the fuse.  Other areas of the circuitry might get a short but the current would be limited by any resistors in the circuit.  Example, say the screen bypass cap shorts,  normally this would not blow a fuse, instead you would see the screen resistor smoke.  A short on the filament line would probably blow the fuse.

Fred

Parasitic or other type oscillation?

I'm not sure the time constant of the kill a Watt.....   But is it fast enough to show?

A thought.

--Shane
KD6VXI

What I did notice tonight is that on pin 6 of V3, 6146 gives me a dead short to ground. Shorted C14 capacitor? See close up of this area attached.

I'm not sure if it is parasitic or other. It changed so rapidly, you'd miss it if you blinked. How can I tell the difference?

I don't know about the Kill-A-Watt either.

Pins 1,4 and 6 are all connected together internally in the 6146.  Pull out the 6146 and measure each socket terminal.  These three terminals also may be tied together at the socket.  You should be seeing about 8 ohms on one of them unless they're all tied together at the socket.  Check the meter switch, move it to grid and back to plate.  Check the wires going to the switch,  there may be something shorting along the wiring.

Even if there is a dead short on any of those pins it would not cause the fuse to blow.  In fact the only thing that would happen is the plate current meter wouldn't indicate any current. The xmtr would still continue to operate.  OTOH if you find a shorted wire somewhere,  you might find other bad wires at the same location that could blow fuses.

Fred

I took another look at the schematic,  If there was a short on the meter-switch wires that go to the grid circuit that would cause the fuse to blow.  A short there would short the bias supply and the 6146 would lose grid bias.  The tube would draw heavy current along with the shorted bias supply would blow the fuse.  Check the slide switch, it's rare, but it may be shorting to the frame.

Fred

If you suspect C18 or are having problems finding 2kV/3kV replacements for the plate coupling capacitor I highly recommend the Cera-Mite series from Vishay/Mouser such as:

http://www.mouser.com/ProductDetail/Vishay-Cera-Mite/564R75GAD10/?qs=IJbG%2FWJQIdLNaDusJv1gGw%3D%3D

Assuming no leaky capacitors in the power supply, what Fred said AND take another look at the Final's screen voltage in CW and AM mode.

I use up to three volt meters to check voltages in real time.

As far as the grid voltage on pin 2 of the 6DE7, I have seen anywhere from 30 to 50 V.

The important thing is how much voltage is being seen on Pin 3 of the Final. This static voltage in AM mode will vary between 55V and 85 volts, depending on the gain of the 6DE7.

The Final's screen voltage in CW mode should be kept below 180V, and preferably 170V. I routinely replace R18 with a 15k 2W.

Do we know if the Circuit Breaker is functioning properly. If the unit has been abused the CB may be faulty.


Like Fred, I am a big fan of SGM transmitters. :D

Hang in there, you'll get it working.  8)

Phil - AC0OB

Inspect the switch wafers for any carbon tracking.  Any contact cleaner that leaves a residue on the wafers has a potential to carbon track especially any contact that has HV on it.  

As shown in the Modified Power supply, I use a 3A FB for testing and a 3A SB for operation.

I calculated the VA at 230VA so 230VA/120V = 1.9 amps operational and ~2.8 Amps surge.

Phil - AC0OB

Folks, I stepped away from this for a few days being my daughter went back to school yesterday.

OK, I replaced the Grid/Plate switch and all .005uF caps on V3 (6146). There is no change.

Tomorrow I am going to pick up some 3A slo-blows and see if in fact the circuit breaker is faulty and I may have already corrected this problem.

Guys! I removed the circuit breaker and installed a 2 amp fuse. The radio is loading up. It was either one of the .005uf caps on V3 or the Grid/Plate switch that fixed the problem.  I will post my voltages tomorrow because I still have the original issue with some voltages being off? Maybe it's not a problem, you can tell me.

I wish that I could shadow one of you when you work on a radio, you guys have so much knowledge and I learned so much from you in this thread, thanks so much!

Anyway, until tomorrow....

73!

A 1950s ARRL or E&E handbook is also a good resource for understanding vacuum tube technology, especially the chapters covering transmitter & receiver construction.

The oldest ARRL Handbook I have is from 1977, but I do have the 2nd edition of the Abraham Marcus book, Radio Servicing from 1954.

R,


Go here.                             http://www.tubebooks.org/technical_books_online.htm


Do it for the children.


klc

Whoa, awesome! Tnx OM!

Glad you're making progress.  None of those .005 caps on pins 1,4 and 6 would have cause the fuse to blow.   Do you still read a dead short on any of those three pins or has that short disappeared??  Do some transmitting,  see how things go.  If the fuse blows again, we have more work to do.

Most of us learned troubleshooting skills by doing just what you're doing.  The only difference is most of us did back in a day when there were no forums like this one to get some help.

Anyways, I think I can say that most of us enjoy helping out another ham with their project.

Keep the questions coming, someone here should have the correct answer.

Fred

back in the tv/cb shop daze, the tab mount chassis circuit breakers were commonly replaced items ....seems that after a while they trip on lower currents than rated for .... they went away but not until many were installed in new tvs

I still have a pile of those tab mount circuit breakers.

I'm watching this with great interest !!

Bob  W4RFM gave me a DX-60 and it's in the que for putting on the air.

Don W4DNR

OK, here is my latest update:

My  Bias voltage is -80 in standby mode, here are the readings with a crystal in AM position. Reference is what is published on the schematic.

V1 6CL6 Crystal Oscillator
V2 6CL6 Driver
V3 6146 Final Amp
V4 6DE7 Modulator
V5 12AX7 Speech Amplifier

V2 and V4 is what I am concerned about? I don't have the VFO connected, but those readings would be way out. Is it normal to see such a variance between a rock and VFO? Need I worry or just get on the air and have funnnnn?!

XTAL V1 Pin 6 = 278v         REF V1 Pin 6 = 310v
XTAL V1 Pin 8 = 193v         REF V1 Pin 8 = 215v
XTAL V1 Pin 9 = -24v         REF V1 Pin 9 = -25v

XTAL V2 Pin 6 = 298v         REF V2 Pin 6 = 340v
XTAL V2 Pin 8 = 22v          REF V2 Pin 8 = 12v
XTAL V2 Pin 9 = -29v         REF V2 Pin 9 = -115v

XTAL V3 Pin 1 = 0.5v         REF V3 Pin 1 = 1.2v
XTAL V3 Pin 3 = 74v          REF V3 Pin 3 = 65v
XTAL V3 Pin 5 = -27v         REF V3 Pin 5 = -38v

XTAL V4 Pin 1 = 684v         REF V4 Pin 1 = 720v
XTAL V4 Pin 2 = 68v          REF V4 Pin 2 = 25v
XTAL V4 Pin 6 = 68v          REF V4 Pin 6 = 25v
XTAL V4 Pin 7 = -2.9v        REF V4 Pin 7 = -1.0v

XTAL V5 Pin 1 = 128v         REF V5 Pin 1 = 135v
XTAL V5 Pin 2 = 0.1mv        REF V5 Pin 2 = 0v
XTAL V5 Pin 3 = 1.3v         REF V5 Pin 3 = 1.3v
XTAL V5 Pin 6 = 83v          REF V5 Pin 6 = 80v
XTAL V5 Pin 7 = -0.7v        REF V5 Pin 7 = -0.7v

Good work Rik.  You're doing OK.  Learn by doing.

If the rig loads up and transmits ok you're probably OK at this point. As long as there's no smoke you're good to go.   

I would expect some voltage differences with a rig of this age and tubes of today.  most of those voltage numbers are within 10% and you'll have some variation to some extent due to the tubes themselves.

Are these measurements Keydown on 80 meters?

Were these measurements taken at the bottom of the inductors' at the RF shunt caps?

What is your power out?

They look fairly close to what I have seen in DX-60's.

http://amfone.net/Amforum/index.php?topic=40809.0


Phil - AC0OB

Tnx to all for your assistance! I have two questions.

1- Can I use this DX-60a to excite my AL-80 amp? Do I have to do anything or just hook it up and go?
2- Can I put the PS back to the way I had it? Right now I returned it to stock with only one cap. See attched images.

You should have some way (a scope) to monitor your modulated transmitted output and a way to key both the DX-60A and the amp at the same time.

This is the way it is for the DX-60A. If it's working, leave it.

Here is a block diagram for setting up your DX-60:


Phil - AC0OB

Tnx to everyone, I think the rig will be FB now.

Phil, Tnx so much. I apologize because I just saw your last post now, I must have missed the email alert that I normally get when someone posts to this thread.

73 all,

Rik
w2rik