The Repair of a completely destroyed Kenwood TR-2300

On a local Ham Radio Flee Market I saw for 5 or 10 € a Kenwood TR-2300 QRP 2m portable station. It was no batteries pack in, no manual, and it was no microphone with. I don’t know it’s working or not. But this old TR-2300 are sold on eBay for up to 80€ in good condition and without batteries. So I bought it.

At home I saw that this radio was completely destroyed. Some IC’S and transistors fail out of the radios, as soon I opened it. So a long repair is starting…

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At first I start to replace the parts on the upper side (with the speaker)
I saw that the voltage regulator (7805) was broken and the full 12 V came to the IC’s.
It was a little 78L05 (smallest one with 100mA) what I replaces with a big 78S05 with 2A. I cut off the cool sheet, so it fits in. That regulator don’t broke any more. I replaces the other little transistors in that area. Then I replaced the Audio IC (UPC575C2), after that I hear the first rush again out of the speaker. But no station and no output. The final i let in in this time. It was to early to change that, so far.

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Then I checked all the frequencies around the PLL circuit. No Frequency was measurable.
At first I changed the IC in the right. But that doesn’t help.
So the PLL IC was broken too. That was very hard. The original was a SM5104GA. It was not to buy any more. I saw sone for big money in eBay, but that was me too expensive.
After some days in the internet I found a 12,5 KHz modification from UK, where the PLL is replaced with a MC145106, that I got from China for 6€ with shipping. So nice, I got a PLL and 12,5 KHz modification.

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After 4 weeks the MV145106 is arrived. I solder the old PLL out and I saw that the new one is bigger and has more feet. I read again the modification and I know now, what I have done to me 🙂 Cut Pin x to y off and solder it on the place z, and so on…

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Detail view of the new PLL

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It take 4 hours to build this PLL in. But after that I have the frequencies at the check points.

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For the switching of the +12,5 KHz, I use the AUX Switch.

After a complete alignment of the PLL and the receiver, I hear my first stations on 2m.
I made a break for some days and enjoy the moment. But no output in transmitting, so far.

I checked now the final transistor. He was broken too. So I find one in UK for 12,74 € with shipping. After the replacement and alignment of the transmitter, 1,5 Watts with batteries and 2 Watts with power supply came out. I was very happy 🙂

I tried to make a QSO on 145.700, but the frequency on the channel switch was not the same what I saw on my frequency counter. But the most off the channels was OK.
What happens now?

I find out that the resistor network (under the PLL) was broken. So I removed it ad tried it with out. Damn it works 🙂

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And kow I need a batterie box. I find one by Pollin for 1 € what fits in the place in the TR-2300. The accumulators are 1.2V 2500 mAh.

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As microphone I take a Peiker Mic, out of my box.

I made today (01.02.2015) my first QSO’s on a local frequency. It was great ! The receiver is very sensible and the modulation is clear and loud.

Here you can download the 12,5 KHz modification for the TR-2300: TR2300-12k5-step-mod-GB

Here you can download the service manual for the TR-2300: TR2300_serv

That was the costs for the repair:
Accumulators (Pollin) 12,50 €
Batteriebox (Pollin)1,00 €
78S05 (out of my box) 1,00 €
other parts (R,C,Tra.) (out of my box) 3,00 €
74LS73 (Ebay) 0,80 €
MC145106P PLL (eBay China) 6,00 €
IC UPC575C2 (EBay) Audio 4,45 €
2SC2329 Final (EBay UK) 12,74 €

Together: 41,50 €, so I got a TR-2300 for a little over 50 € and I had a lot of fun with the repair. That’s OK for me.

But the work, you can’t pay.

 

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