1. Remove top and bottom covers.
2. Remove the top screw from each side of the front panel assembly.
3. Carefully rotate the front panel forward to gain access to the control board(x53-3560-11 a/4). This board is mounted vertically against the body of the transceiver. It is not the board that is mounted in the front panel assembly.
4. Locate and remove resistor R244 from the control board. R244 is below IC12 ROM and above IC23. There are two chip resistors, one on top of the other -carefully remove or break the top one..it is easily fractured -that's R244.
5. 5. Reassemble and then perform the cpu reset by holding the A=B button depressed as power is turned on.

1. Remove the bottom cover of the TS-870S
   
   
2. Remove the shield that covers the TX-RX board which is located on the right side of the bottom of the transceiver.
   
   
3. Carefully remove IC4, IC5, & IC6 from their sockets and replace them with the new parts listed above.
   
   
4. reset the transceiver by holding the [A#B] key depressed as power is turned on.

1. Make sure the pins of the new EPROMs are properly aligned before insertion. New EPROMs tend to have the pins spread aout wider than the socket. The pins can be beat in by pressing each side of the EPROM against a static free work surface.
   
   
2. Avoid touching the EPROM pins. Graps the device from the top and bottom epoxy body ands between thumb and forefinger.
   
   
3. Avoid inserting the EPROMa backwards.

RF PCB:
R157         1,8K  to  560      RK73FB2A561J
R160,161     2,2K  to  1K       RK73FB2A102J
R164         1.5K  to  560      RK73FB2A561J
R169         1K    to  330      RK73FB2A331J
L76,79       3.3u  to  0        R92-0670-05

TX-RX PCB:
R332         2.2K  to  6.8K     RK73FB2A682J
C340         .022u to  .01u     CK73GB1C104K
VR1          470   to  3.3K     R12-6737-05 (optimal)

1. Remove the bottom cover and shields anclosing the RF board and TX-TX board.
   
   
2. Replace L76 and L79 on the component side of the RF board.
   
   
3. Replace C340 and R332 on the component side of the TX-RX board.
   
   
4. Access the bottom side of the RF board and replace R157, 160, 161, 164 and 169.
   
   
5. Perform S-Meter alignment step 8, on page 95 of the Service Manual. If you cannot obtain "05" of the display, replace VR1 on the TX-RX boardwith the part listed above.

I loved the TS-870 when I first got it. Size is ideal for expedition radio, light weight, fits in carry on luggage. Features and computer controls are excellent, until I used it in the contest on 160m. Bloody thing got overloaded with signals 4 kHz away. Everybody was QRMing me! What a piece of blinking junk! Liking the radio otherwise I inquired at Kenwood about the problem of overload. They came up with modification to remedy the gain distribution in the RF and mixer stages, which was implemented in later production models. After I received the service manual, I started to dig into the radio and came up with few more improvements.

Earlier production units before S/N 801xxxxx had problem with front end overload and consequent distortion and crossmodulation in the later stages, including DSP, especially noticeable on low bands. To remedy that on those earlier units see the Overload Modification.

There is an absence of 2nd RX antenna switching (Beverages, etc.). When I inquired at Kenwood, they supplied modification instructions that required some drastic modifications, including cutting the traces. When I obtained service manual, I figured very elegant modification using just plug in diode. See 2nd RX Antenna Switching modification.

Examining the circuits and filtering arrangement, I have found that Kenwood engineers decided to rely on obtaining the selectivity mainly by using the DSP. Theoretically it is great, except when strong signals blow by the mediocre crystal filters used in stock TS-870, they modulate the following stages, including DSP circuits. The biggest improvement that puts this radio one class higher, is to replace the stock 2nd IF crystal filter and 3rd IF monolithic ceramic filter with high quality International Radio or other filters. Any better shaped filters make tremendous improvement to the selectivity, overload and DSP performance. Depending on intended use, you can use 2.7, 2.4 or 2.1 kHz bandwidth filters. I chose 2.1 mainly for contesting purposes. It is possible to use narrower filters for CW operation, but selectivity selection scheme via microprocessor controlled switching makes it complicated and throws the controls off their markings. I found that 2.1 filters work very well even for CW and are significant improvement over stock arrangement. See Filter Modification.

Overload Modification

NOTE: the changes do not apply to radios with S/N 801xxxxx and later.

Adjustment:

2nd RX Receive Antenna switching modification

Kenwood TS870 has two antenna jacks ANT1 and ANT2 and external receiver antenna jack (RCA type) that can accommodate external receiver when activated through the program menu. This adds some attenuation to TS870 receiver signals. There is no provision for external receive antenna switching (Beverages, preamp., etc.) When I inquired Kenwood about this option, they sent me modification instructions that required cutting the traces and rewiring the ext. RX connector. When I received my Service manual and had a look at the circuit, I came up with this simple modification:

Parts needed: 1 diode (any type) I used rectifier diode, generic NTE125

1. (In the following references the front panel of the rig is facing you.)
   Remove the top cover.
   
   
2. Remove 7 screws holding the cover over the FILTER and RELAY unit (in the middle) and remove the cover. (Where the ANT1 and ANT2 connectors go.) This exposes two PC boards.
   
   
3. Locate the connector CN301 on the RELAY unit (adjacent to ANT1 and ANT2).
   It is about 1 inch back and 1 inch left from the ANT1 connector and has three wires going to it - two gray, left and one black, right.
   
   
4. Take the diode, clip the leads to about 0.5 inch length, bend them down and form them so they are spaced about 1/8" and parallel (kinda forming letter Y).
   
   
5. Plug the diode into CN301 connector from the top, pushing the diode wires between the plastic housing and the metal contacts of the connector. Cathode (the end with the band marking) of the diode should go to the middle contact (gray wire), the other end to the left contact (gray wire). Make sure that diode makes good contact with terminals of the connector. Black wire should be free.
   
   
6. That completes the modification. Replace the covers, do not pinch the wires going to the antenna tuner!

Operation:

Connect your transmit or main antenna to the ANT2 connector. Connect your receive antenna or preamp output to ANT1 connector. Now you can transmit only through ANT2 connector.
Front panel button ANT now allows you to select ANT2 (receive/transmit on ANT2) or ANT1 (receive on ANT1, transmit on ANT2). Antenna tuner would always see the impedance on ANT2. The way the switching works, whenever you transmit, you will switch ANT2 on transmit, regardless of ANT1 or ANT2 selection. Much better use of connectors than originally devised by Kenwood

Notes on TS870 usage: Normally there is enough gain on the receiver for beverages. In case that you need to use the preamp or preselector, than turn the AIP on TS870 on, and if needed add the attenuators. Try to keep the noise level peaks close to low end of the Smeter scale. Helps with intermods. If using DSP, play with different settings and different levels of AGC setting, it has effect on overall behavior.

Filter Modification.

Major improvement in selectivity and DSP performance can be achieved by replacement of 2nd and 3rd IF filters with sharp crystal filters, like from International Radio. The 2nd IF 8.83 kHz filter used in TS870 is the stock Kenwood crystal filter, while the 3rd IF 455 kHz filter is little ceramic Murata filter.

I have ordered set of 2.1 kHz filters (8.83 and 455) from IR. The modification involves removal of printed circuit boards where the filters are located, unsoldering the old filters. In their place solder short piece of miniature coax to connect new IR filters. IR filters can be mounted between the circuit boards and the metal chassis using double sided sticky tape. Coax from old filter connections is then connected to new filters. Tweaking the matching IF transformers next to the filters ensures proper match and gain.

Other filters with wider bandwidth can be used also. For contesting I found 2.1 filters to be the best and the mod works very well on CW also. Selectivity improves as well as functions of DSP. Now it is a decent radio, matching those costing thousand(s) more.

Good luck and I am not responsible for any goofups you make! :-)

When I got the TS870S first I was really not amazed about the selectivity, also not about the quality of the build-in front end. But the filter-mod and also Kenwood$B!-(Bs front-end-mod helped to solve these problems. But there was one additional possibility to improve something. When I reduced the output power to drive a bigger linear, I found, that the ratio is changing between SSB in comparison to modulate with a single-tone. If the percentage was 50% between voice and CW using 100W output before, the ratio is dropping down if you are running only 10W (measured with a peak-meter).
That is not very helpful, because it$B!-(Bs not easy to drive the linear correctly in that case. And you can$B!-(Bt improve that using higher microphone gain or processor. The reason is Kenwwods ALC-curcuit (it$B!-(Bs simmilar to the TS50S) which can be found on the RF-unit. In the curcuit diagram it$B!-(Bs named "Reserve Current Prevention". This part is directly controlling the TX-amplifier Q39. And this part has normally nothing to do with the power adjustment or regulation. But using lower output it$B!-(Bs more sensitive and therefor more effective.

Turn your TS870 on it$B!-(Bs head (foots up) and remove the cover. If the display is looking into your direction, the big curcuit board on the left-hand-side (underneath an additional metallic shielding) is the RF-board. Remove all connections carefully and afterwards the complete board. There are 3 electrolyte capacitors named: C286, C287, C289. Place a small resistor (I used a small chip-resistor) with 1 KOhm in parallel to C289, which is in the middle. Best is to do that on the soldering side (not component side).
That$B!-(Bs it ! Bring the TS870 back to live and afterwards you will see the improvment in SSB-mode and you can easily measure it. Everyone told me afterwards, pumping effects are gone and my voice sounds fresh and clear (is that possible with an age of 40 ?)
If you are only running your rig with full output, it$B!-(Bs not neccesary to realize this mod. In my case I am going down to 5 Watts - afterwards I$B!-(Bm driving an attenuator going down to 20 mW (-24dB) and this is driving a commercial russian linear with the possibilty of 2KW out (+50dB). Therefor it$B!-(Bs absolutly necessary to have stable conditions.

There are output power setting procedures in the Service Adjustment Mode Menu.

In the adjustment mode there are 28 menu numbers A0 to BB (hex). All adjustments are saved in the EEPROM. When the service adjustment mode is entered, data is read from the EEPROM and placed in the CPU RAM so that settings can be modified.
The EEPROM is updated only when data is written in Menu No. bA (hex).
The Service Adjustment Mode Menu is a hidden menu.

OPERATION PROCEDURE

1. Connect a >100W 50 Ohms dummy load to the antenna terminal
   
   
2. Hold down the [N.R.] and [LSB/USB] key (together) and turn the [POWER] switch ON to enter the adjustment mode. The menu number will appear in M.CH on the display
   
   
3. When the 'M.CH/VFO.CH' control is turned the menu number changes. Turn the control knob to menu number 'A7' (100W Power adjustment)
   
   
4. Press the PTT key to transmit and while transmitting turn the 'RIT/XIT' knob to a desired power level (i.e. 120W). Don't use a power level >140 Watts!
   
   
5. Press the [UP] key to confirm the new power level setting (don't forget it!).
   The menu line should show two equal hex numbers. For example 120 W output power:
   A7 b2 b2 PWR 100W. The second 'b2' is the local confirmation for your setting.
   
   
6. Turn the 'M.CH/VFO.CH' control knob to menu number 'bA'. The menu shows now:
   ba rEADy EEPROM
   
   
7. Press the [UP] or [DOWN] key to store the new settings into the EEPROM.
   
   
8. Press finally the [CLR] key.

Note: When the [CLR] key is pressed before pressing the [UP] or [DOWN] key or power is switched OFF in the adjustment mode, all new settings are canceled.

Do not use a power level >140w! your work is at your risk! i do accept no responsibility!

Good luck,

73, Werner
DJ2HZ / VE7HBI
http://www.ginko.de/user/wsz/index.html



07-05-2000 TS870 external receive antenna switching
Author: Yuri Blanarovich - K3BU - [email protected]


Kenwood TS870 has two antenna jacks ANT1 and ANT2 and external receiver antenna jack (RCA type) that can accommodate external receiver when activated through the program menu. This adds some attenuation to TS870 receiver signals. There is no provision for external receive antenna switching (Beverages, preamp., etc.) When I inquired Kenwood about this option, they sent me modification instructions that required cutting the traces and rewiring the ext. RX connector. When I received my Service manual and had a look at the circuit, I came up with this simple modification:

Parts needed: 1 diode (any type) I used rectifier diode, generic NTE125

Step by step instructions:

1. (In the following references the front panel of the rig is facing you.)
   Remove the top cover.
   
   
2. Remove 7 screws holding the cover over the FILTER and RELAY unit (in the middle) and remove the cover. (Where the ANT1 and ANT2 connectors go.) This exposes two PC boards.
   
   
3. Locate the connector CN301 on the RELAY unit (adjacent to ANT1 and ANT2).
   It is about 1 inch back and 1 inch left from the ANT1 connector and has three wires going to it - two gray, left and one black, right.
   
   
4. Take the diode, clip the leads to about 0.5 inch length, bend them down and form them so the are spaced about 1/8" and parallel (kinda forming letter Y).
   
   
5. Plug the diode into CN301 connector from the top, pushing the diode wires between the plastic housing and the metal contact of the connector. Cathode (the end with the band marking) of the diode should go to the middle contact (gray wire), the other end to the left contact (gray wire). Make sure that diode makes good contact with terminals of the connector. Black wire should be free.
   
   
6. That completes the modification. Replace the covers, do not pinch the wires going to the antenna tuner!

Operation:

Connect your transmit or main antenna to the ANT2 connector. Connect your receive antenna or preamp output to ANT1 connector. Now you can transmit only through ANT2 connector.
Front panel button ANT now allows you to select ANT2 (receive/transmit on ANT2) or ANT1 (receive on ANT1, transmit on ANT2). Antenna tuner would always see the impedance on ANT2. The way the switching works, whenever you transmit, you will switch ANT2 on transmit, regardless of ANT1 or ANT2 selection. Much better use of connectors than originally devised by "knowitalls" at K...d.

Notes on TS870 usage: Normally there is enough gain on the receiver for beverages. In case that you need to use the preamp or preselector, than turn the AIP on TS870 on, and if needed add the attenuators. Try to keep the noise level peaks close to low end of the Smeter scale. Helps with intermods. If using DSP, play with different settings and different levels of AGC setting, it has effect on overall behavior.

TS870 looks like great contestpedition radio, it's light, fits in carry on luggage. I got speech module for phone CQing and small switching PS for it ($160). I still miss the tunable audio peak filter and ability to go lower than 400 Hz on CW note.

Good luck and I am not responsible for any goofups you make!

Yuri Blanarovich,
K3BU, VE3BMV, P40A, one of N2EE
[email protected]




07-05-2000 [CQ-Contest] Collins Filters in Contest Rigs
Author: Yuri Blanarovich - K3BU - [email protected]

In a message dated 98-08-11 11:27:17 EDT, K2AV writes:

<<  The Collins filters vary quite a bit. In the ft1000mp, the Collins 500
 hz filter (455 if) and (the CW soldered in) Yaesu 500 (8m if) cascaded
 are significantly less selective and less deeply skirted than the INRAD
 400 hz filters for both IF's cascaded. If you want to hear the
 difference, let me know and we can arrange a telephone call, and I can
 let you *listen* to the difference.
    In the 160 meter cw test I got between stations up & down 500 hz that
 are 20 over s9, and the INRAD cascade renders them *inaudible* unless
 they have key clicks. The difference after I switched was stunning. Hard
 to believe, but I am afraid that some of these new Collins filters seem
 quite inferior to the Collins of old.
  >>

Same experience here, I tried Collins and Inrad filters in TS870 and Inrad filters seem to work better. One difference is 400 vs. 500 bandwidth and it also appears that design and packaging has changed. I was surprised by the small size of late Collins filters. Maybe technology advanced and shrank the components. The only way to test or compare is to do some plotting of the bandpass curve for various filters in your radio and do some comparison.
In TS870 the DSP seems to skew the results, it contributes to the shape of filter curve - DSP seems to "improve" it and mask the true bandpass. The best thing is to measure the signal after the filter's IF buffer stage, before detectors and DSP stages. (Or use the network analyzer for those who have access.)
Sometimes even the "same" filters have different characteristics, manufacturing tollerances can play games here.

The best CW filter I have seen so far is the Collins 300 Hz 455 kHz IF crystal filter. Amazingly it has less attenuation than wider Kenwood and Inrad filters and very sharp skirts.

When considering replacement/addition of filters one has to look at impedances too. In some cases buffer amplifiers or matching devices should be implememnted and in case of cascading the same filters in particular IF, buffer amp might be needed to boost the insertion losses from additional filters. The most benefit is obtained from cascading sharp filters at the closest possible IF stage to the front end.

For the real rock crush proof front end there 50 ohm custom impedance filters available (INRAD) for custom design frequency. Great for those with their "own" CQing frequency. I haven't used them yet, but heard that some JA stations in metropolitan areas were using them.

Generally, if one wants to improve the receiver, the first thing should be to consider replacing the "stock" filters with better ones - gives the most bang for the money. Looks like some manufacturers are leaving this door open for upgrades by leaving enough room in the IF PC board stages area for extra and larger filters (Yaesu, Icom).

73 Yuri Blanarovich, K3BU, VE3BMV



07-05-2000 Use TS-870 as a contest rig
Author: Vladimir - [email protected]


Hello,
To whom who would like to use TS-870 as a contest rig, I would insistently recommend to make three proper mods, that I recently did (Geat TNX to Yuri K3BU/VE3BMV).

The first is intermod mod available from Kenwood for S/N below 801XXXXX.
This modification shifts gain distribution from RF stages to IF stages. Involves changing of about 8 resistors.

The second is filters mod. Yuri recommends to put two 2.1 KHz INRAD filter instead of two 3 KHz filters for both 8.83 and 455 IFs. I don't have INRAD fliters, so I replaced both (8.83 and 455) 3 KHz filters for another Kenwood filters 2.4 KHz: YK-88S-1 (the same size) and YG-455S-1 (needs much more free space and two coupling capacitors to avoid DC short circuit). These filters are quite good compromise due to the mixing and shifting scheme for various bandwith. I ploted curve for original filter and new, the slopes were about the same due to DSP action. But there is a big difference in overload and intermod due to strong adjacent signals from edges of the filters. DSP is too late after the IF chain, strong signals outside of DSP bandpass but inside of filter bandpass will "pump" the stages ahead of DSP and "confuse" it. This is why good filters make huge difference.

The third is external receive antenna switching mod. After this mod : when "ANT2" is selected - Ant2 connector is for both TX and RX, when "ANT1" is selected - Ant2 connector is for TX only and Ant1 connector is for RX only, i.e. I can use another external antenna for RX.

So, after all these mods done I estimate my rig's job like excellent.

73 Vladimir ("Bob") UT1IA
[email protected]