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IFR COM-120B not charging internal battery

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AdrianH
Posts: 24
Joined: Fri Mar 16, 2018 12:03 pm
What radios do you own?: Yaesu FT-857, FT-902DM, FT70

IFR COM-120B not charging internal battery

Postby AdrianH » Tue May 08, 2018 10:55 pm

If anyone recognises the fault I would be grateful.

The unit runs OK on Mains, will work OK from the internal battery when charged externally, and will power from external DC. Just will not charge the internal battery.

So if anyone know the circuit enough to point me in the correct direction, not sure what the charging circuit could be, may even be a as simple as a limiting resistor or Transistor limiter etc. Diode etc but without circuits I hate just diving in blind.

Many thanks

Adrian

lc4600
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Re: IFR COM-120B not charging internal battery

Postby lc4600 » Wed May 16, 2018 1:07 pm

The 14 volt oven supply is used to charge the battery when the oven heat up current rolls off(R56-.43shunt and Q13-2N2907).Q13 will then turn on Q3(irf9540) and apply charge current to the battery thru CR16(mbr1645) blocking diode.
Carl N0PXJ

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AdrianH
Posts: 24
Joined: Fri Mar 16, 2018 12:03 pm
What radios do you own?: Yaesu FT-857, FT-902DM, FT70

Re: IFR COM-120B not charging internal battery

Postby AdrianH » Thu May 17, 2018 3:48 am

Thank you Carl I will have a look at mine and see if I can follow the line you mention.

Although I have to ask is the oven there if no option 2?, think I just have the standard 10 MHz, but it will give me something to look at.

Adrian

Jim202
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Joined: Sun Sep 09, 2001 4:00 pm

Re: IFR COM-120B not charging internal battery

Postby Jim202 » Thu May 17, 2018 4:23 am

The other possibility is the battery is old and has not longer any life left in it. One more possibility is the battery was left dead for too long of a time and you can no longer charge it.

I have played with rechargeable batteries for many years. Some can be brought back to life and others is like a dead horse. Once it's on the ground it will never get back up.

I use a variable voltage power supply and connect the battery to it. This way I can watch the voltage as well as the current. You will have to use a voltage above the battery voltage to get it to even start to take a charge. Normally the battery internal resistance is really high after it has been dead for any period of time. You have to get passed this to get it to charge.

Don't get the battery hot while trying to charge it. I generally have found that if you can get the current up to an amp or so, you might stand a chance to bring it back to life. But don't keep the current that high for any extended amount of time. Remember heat is the battery's worst enemy. Keep a close watch on the battery temp.

Once you can get any voltage to stay in the battery, now you can try to get it to provide some current. I have several resistive loads I have made up over the years. Sometimes just the 10 amp scale of my Fluke digital meter works well. I just put the meter in the 10 AMP. DC position and short the battery while watching the current. You will see the current slowly start to go up and then start to drop. Once you see the current start to drop, stop and go back to charging it.

If you can get the voltage up, you will need to use the resistive load, as more than a few cells working can cause damage to both the cells and the meter if the current gets above an amp or so.

Bottom line here is if the battery is old, you stand almost a zero chance of bringing it back to life. Get on Amazon and find a replacement.

Jim

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AdrianH
Posts: 24
Joined: Fri Mar 16, 2018 12:03 pm
What radios do you own?: Yaesu FT-857, FT-902DM, FT70

Re: IFR COM-120B not charging internal battery

Postby AdrianH » Thu May 17, 2018 5:03 am

Hi Jim;

the battery is a new one I bought very recently as I knew the original was dead.

I will take the thing apart and look later.

Adrian

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AdrianH
Posts: 24
Joined: Fri Mar 16, 2018 12:03 pm
What radios do you own?: Yaesu FT-857, FT-902DM, FT70

Re: IFR COM-120B not charging internal battery

Postby AdrianH » Thu May 17, 2018 2:21 pm

Well I have had a look and I am none the wiser, well perhaps I am. The PSU has been repaired in the past and seems to have replacement Electrolitics in it and a few replacement Tant's where the power connector is to the rest of the unit.

I found it very difficult to see markings on some of the components as the boards have been lacquered and there are no markings such as Q13 Q3 etc to determine which components are where?

I buzzed around with a meter and checked diodes etc then put it back together. On checking over the very limited information in the manual I noticed Connector 3 on the base of the PSU that should supply the Oven ( it does not have an oven fitted) and there is no 13.8 Volts to the socket J3 so I assume from Carl's information I would have to look as to why.

Not sure if you can power the PSU without the on off connections from the front so not sure at present how to go about this.

Carl if still reading at this point can you assist in anyway where I should look what components etc.

I took a couple of simple snaps with the phone, but not really going to show a lot.

Adrian

Image
Image
Image

I have virtually all sorted bar this now I know I can work without the battery but always a nice to have.


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