Here's how to repair a Kenwood MC-59 microphone cable (ships with the TM-V71a, probably the 710, and a few LMR radios as well).
First, if you didn’t know already, behind the rubber boot at the end of the Kenwood MC-59 mic cable is a regular RJ-45 jack:
Step 0. If you want to avoid all this, the cord is part Kenwood E30-7543-18 at PacParts.com. (They also ...
To me, this looks very much like a "DIN Lautsprecherstecker":
Positive is the small hole, negative the wide slot.
Loudspeaker, if I ask google, is zvočnik in Slovenian – so the "ZV" label makes sense; you can switch between speaker pair 1 and 2.
I would suggest that these were probably designed to run dry or very lightly oiled (ie: no grease) and that some previous owner took it upon them self to "fix it" using the wrong grease. There will most certainly not be such a thing as a grease specific to Morse keys. (So a quick internet search for "precision bearing lubricant" will give you more info than ...
So far as I'm aware, the reason for using a variac isn't that there are tubes, but that the radio is old and unused for a long time.
The reason is that electrolytic capacitors rely on a dielectric (insulation between the plates) that is maintained by an electrochemical reaction between the plates. This reaction requires a voltage across the plates to occur. ...
With the battery case detached from the device, look at the side with the copper terminals. You should see several seams that can be exploited with a sufficiently thin shim. I carefully used a box cutter on the right hand inner seam of the battery case and separated the battery case into two pieces without actually cutting or breaking any of the small ...
Are you sure that you are correct in the comments about your pin 2 and pin 7? (The conventional numbering for these tubes is as in your drawing, so conventionally pins 8 and 5).
If you look very carefully or use an ohm meter you might find that your pin2 is actually the cathode and your pin8 is G1, as in your drawing of the 6L6.
This would be more normal ...
I found the TM-741A service manual. As shown on page 106, the battery can be seen looking into the case from the front after the display panel is removed. Luckily, the spare batteries from my dive computer will work; now I just have to open the radio and solder in a replacement!
LEVI means LEFT
DESNI means RIGHT
ZV1 is speaker one
ZV2 is speaker two
S this radio has connections for two pairs of 4 ohm speakers. I guess LEFT ZV1 and RIGHT ZV1 are main speakers and ZV2 are additional (as option).
Each speaker connector is DIN speaker connector with two contacts. Wide contact is speaker minus, circular contact is speaker plus pole.
The transformer is most probably a part of a critical tuned circuit. If the ferrite is broken then the radio keeps working but the filtering is worse.
There a a number of ways to find a replacement for the transformer.
1: Try to get the technical manual and find the partnumber and supplier (manufacturer)
2: Look for the information on the pcb and try to ...
The process is called degassing. This is done to prevent arcing in high voltage transmitting (power amplifier) tubes. It is not as important for lower voltage tubes but I am sure if done correctly no harm should result.
To degas you preheat the tube when it has been inactive or in storage for a long period of time. Residue of gas is removed or absorbed ...
I have to ask the obvious question: is the antenna tuned when you are trying to receive? Briefly transmitting may activate an automatic tuner.
Relay contacts sound like a reasonable hypothesis, though there could be plenty of other things.
You might try hooking up a dummy load, turning the power to minimum, and going through many receive/transmit cycles. ...
Tecsun is very similar to Baofeng in that anybody selling them expects a certain number of DOAs and other failures. They already know that QA on those rigs is directly reflected in the price.
In the past I have had good success with getting vendors of like this to replace the radio body (no battery or antenna) simply by writing to them.
I have gotten ...
At HF there are almost no limits on how bad your splice can be, as long as:
there's no short circuit
braid is connected to braid and inner to inner
You could even use a "chocolate block" connector :)
* photo from Tudor Barker, cropped
But to do a neat job:
At each cut end, strip about 25 mm (1") of the outer sheath, and then about 7 mm (1/4") of the ...
Referring to the circuit diagram for this set
The mic connector has 2 pins and the grounded body as the 3 connections.
As you have guessed the 2 pins are mic input (measured at 0 volts) and PTT switch (measured 30 volts). Both return to the body of the connector.
The PTT pin is ...
SSB requires a signal from the microphone: only when you are talking there is a signal generated. For CW you need to connect a morse key or paddle to have output signal. When FM and AM are operational there is nothing wrong with your power amplifier. In case of a defect: check the microphone by listening to the AM or FM output signal and when that is ok and ...
Zeiss, the first step in fixing any radio is usually to check the power supply levels. If the power supplies are wrong then nothing will work properly. I would do that first before doing anything else. Also, when the plate current goes up does one or both of the valves glow brighter and brighter ? These two things will give clues to the fault. The fact that ...
The creap could be a bad capacitor or the circuit is over loaded due to excessive voltage on the plate. This sounds systematic of a component failure and requiring component isolation and L-C meters. You could have any number of bad components. You should be using a VTVM however the main reason is the level of the reading, milli. Sounds simple but first ...
I will answer the final question: "Should I return them to the store?"
If they are still under warranty, return them and get a replacement.
If the battery is a sealed unit inside, then opening them might void the warranty - and if it's not, then chances are it's the charging circuitry that has failed.
Return them and get a replacement - I don't know ...
Take a look at the Owner's manual. You might try connecting an antenna to it, and see if you can hear sounds coming out the speaker with the volume and RF gain turned up. But if the digital readout is dark, something else may be wrong
Here is the Drake TR7 service manual, as well as the Owner's manual.
Chances are you can find what you need here.
Could be you broke the slot without moving the coil core. If that's the case you might be better off to leave it alone.
If you can solder and want to replace it you need a voltmeter and a schematic. Put the ...
Old plastic can crack into tiny bits, ruining everything; however yours doesn't sound that old.
Ideally, silicone grease applied to moving surfaces is the best; it doesn't degrade plastic, lots of things do degrade plastic. Apply to shafts after removing them if that seems best, don't use too much.
Although silicone grease (sold for putting on spark plugs ...
Once cleaned up, a simple light oil, such as 3-in-1 household oil, is sufficient. There is no need to use a real grease or heavy oil, but a light oil will prevent oxidation, reduce wear, and make the action a little smoother than dry bearings.
Note that while this isn't a big piece of machinery, depending on the materials involved and how much and how fast ...