// Home / Amateur Radio / Kenwood TH-D7 Amateur Radio Handheld Transceiver

TH-D7

In 2010 I bought a second-hand TH-D7E because of its full-duplex capabilities for mode U/V and V/U satellite operations. Also the APRS option is a nice feature of this handheld transceiver.

Some pictures from the inside of the transceiver are shown below. The first picture section is about the replacement of the power modules, the second section shows a picture of the extended RX modification.

Documentation and Datasheets

Some documentation for the TH-D7 is shown below, together with the datasheets for the VHF and UHF power modules, for both the original and the replacing power modules.

RF Power Module Replacement

By accident the RF power modules for both VHF and UHF were broken some day, most probably because of applying an external DC power voltage which was too high. Even when the transceiver's power was switched off, the external power is almost directly connected to the power modules. So take care! In my case both power modules didn't deliver any significant power output. Even with the transceiver's power off, a leak current of a few mA was present, caused by the broken power modules.

During the analysis what was wrong about the transceiver, the section about the APC circuit (page 6 of the service manual) was also helpful in my case.

I took some pictures during the replacement process, which might be helpfull to others. Please read the service manual first before opening the transceiver, the pictures below are not a complete description, but just an impression what to expect. The repair process also shows my experiences, any repair is at your own risk.

Opening the TH-D7

TH-D7 just before opening, the battery holder removed. The four Phillips type screws must be removed from the chassis to open the transceiver.



Opening the TH-D7

On top of the TH-D7 the nuts of the Volume/Dial knob and the SMA antenna connector should be removed. The nut on the SMA needs a special tool (who can provide me the name of this type of nut?).



Inside the TH-D7

TH-D7 opened up. Take care not to break the rubber seal on the top of the transceiver. The metal shielding/casing on the bottom PCB must be removed in order to reach the power modules. Therefore two screws must be removed and some de-soldering should be done.



Inside the TH-D7

Metal shielding removed, the 70 cm power module (M67799MA) is directy visible, the 2 m one (M67798LRA) is still hidden between another shielding/casing. I was thinking that maybe the extra casing above the 2 m module is to screen the 3rd harmonic from the 70 cm receiver part (comments on this are welcome).



Original M67798LRA and M67799MA power modules of the TH-D7

Original RF power modules, which are no longer in production. Left the M67798LRA for VHF (2 m) and right the M67799MA for UHF (70 cm). The 70 cm module was opened for curiosity, as it was broken anyway.



New power modules RA08H1317M RA07H4047M of the TH-D7

New power modules, RA08H1317M for VHF (2 m) and RA07H4047M for UHF (70 cm). Both the back and front are at the picture. The top modules are shown the back where is it visible that the back of the modules are not flat as the original ones (see the datasheets of the two modules for the exact dimensions). So take care of the heat dissipation when re-mounting these in the TH-D7!



Original versus new power modules the TH-D7

The original (top) and the new (bottom) power modules. The observant reader will notice the difference in pin layout between the original M67798LRA and the new RA08H1317M modules for VHF. The 'R' means 'reversed' (or similar)! For the new power module series no reversed pins are available. So carefully check the datasheet, and good luck with the mounting! The outer pins are the RF-input and RF-output, the two in the middle are the Gate Voltage and the Drain Voltage, see the datasheets for details.



Power cross wiring of the new RA08H1371M power module

Cross wiring the two power pins on the new 2m module was relatively easy. The 70cm module was not place here yet.



RF cross wiring of the new RA08H1371M power module

The RF-pins cross wiring for the 2m RA08H1371M power module was done by using two small pieces of teflon coax, which could resist the heat while soldering very well compared to regular coax. The shieldings were soldered directly to the power module shielding, maybe a bit of a compromise on VHF characteristics, but very effective in restricted space for mounting and mechanical strength!



RF cross wiring of the new RA08H1371M power module

Another look on the cross wiring. This mounting worked out perfectly fine in the end.



Both new power modules RA08H1317M and RA07H4047M mounted

Both new power modules placed. Mounting the new 70cm module was simple because it is pin-compatible with the old module.



Final power measurements with the two new modules installed

After installing the two new power modules, the RF power output was measured at the center of both amateur bands. The image shows the results for VHF at the left and UHF at the right, and from top to bottom the power levels EL, L, and H. These measurements were performed with an external 12 V DC power supply connected.



Ordering Replacing Power Modules at Mini-Kits (Ham Radio Kits and Components)

After some research on the Internet, the replacing power module types were ordered at Minikits in Australia. Excellent service, the replacing power modules arrived within 7 days in The Netherlands, carefully and customs-proof packed.

Minikits Australia

Customs-proof fast delivery by Mini-Kits Ham Radio Kits and Components from Australia
(Personal information for both parties removed)



TH-D7E Extended RX Modification

On Mods.dk a modification can be found for extending the RX range of a TH-D7E. Below a picture is shown of my TH-D7E where the green wire which should be cut is visible.

TH-D7E Extended RX Modification

The green wire which was cut for the RX extension is visible top-left of the back of the speaker.



Acknowledgements

Thanks to Leo PA0LEZ for leading me through the entire repair process, including hands-on assistance, at his electronics lab at EMCO in Assendelft, The Netherlands. Also thanks to Ronald PA5RB for some general help and advice.

2012-2014 by Ivo Klinkert, PA1IVO - Contact