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R7000 add Bias-T?

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DaveNF2G

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#1
Has anyone seen any mods that would add a Bias-Tee feature to older receivers (non-SDR)? I'd like to enable my R-7000 to power an antenna mounted preamp.
 
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#2
Has anyone seen any mods that would add a Bias-Tee feature to older receivers (non-SDR)? I'd like to enable my R-7000 to power an antenna mounted preamp.
Why don't you just use a bias-T injection block. That way you don't have to tear into the radio. Just use a coax cable between the receiver and the injection block. If you change radios, you just move the injection block to the new radio. It's done all the time in commercial and public safety radio systems.
 
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#3
The Icom all mode such as the 820,821 910 and 9100 amateur radios have this built in but each amp is band specific and drop off line with switching relays while transmitting. Think the injection block or doing this mod to a Stridsberg 8 port would be the better Idea. A single Icom receiver around here would suffer from overload with a wideband amp.

What bands do you need more gain on?


David
 

DaveNF2G

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#4
My R-7000 is slightly deaf due to old age, so I want to put a low-amplification broadband amp on it. I have an LNA4ALL around here somewhere and that's what I want to use if I can find it.

I plan to give the 7000 its own antenna, so no other radios will be using the preamp.
 

DaveNF2G

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#5
I just sent a query to one of the manufacturers who has low-cost customizable units. Thanks for the tip - I had not heard of these injectors before.
 
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#6
If I recall, ICOM published a service bulletin regarding sensitivity problems in the R7000. These receivers have several varactor tuned filters in the front end. If the power supply DC fiktering caps become weak, the varactors get modulated with ripple. So going through the power supply, or testing with a 12V battery would be first test. Secondly, there are adjustment pots for the filters.
 

rbm

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#7
Something like this would work.

The DC Power Inserter is sold on ebay for $4.95 each. Shipping is $3.40 per pair.

The DC Block is around $495 also.

Then, use a wall wart to supply the DC for the amplifier.



Rich
 
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#9
R7000 Display/Sensitivity Problem

Date: 13 Jan 89 19:24:00 GMT
Subject: R7000 Display/Sensitivity Problem

If you are having trouble with you Icom R7000 display being flaky
and then a sudden decress in sensitivity try the following:


PROBLEM: ICOM R7000 radios that are used 24 hours a day for a long time
(2 years ) when shut off the display will become flaky and it
is also possible for a lost in overall gain (3 to 40 db).

SOLUTIONS: Officially there is ICOM ECO SB# 9288-004, attached below.

Unofficially from Tech who repairs R7000
The ECO does help the display problem, but most likely
it is not the problem. *

* note repairing your own radio my void you warranty and only
allow a qualified technician to do the job, otherwise damage
could happen to your R7000. If the VCO does not track then a
major alignment would have to be done after. Check the
ICOM IC-R7000 Service Manual for more details before starting
this repair, and to make sure I have not made any typeing errors
you should get a copy of the ECO from ICOM !

1st SOLUTION:
Replace on the DC to DC Board the following capacitor.
Check the noise with an oscilloscope on both sides of
R3, if the noise is not way down on one side then
replace C2 a 33uf 16V capacitor. Noise feedback
can decress the overall sensitivity of the R7000.

Replace on the Display Board
C19 and C20 a 10 uf 16VDC capacitor

I found that on my R7000 C19 & C20 were the cause of my
display problems. They are 10 uf eletrolytics capacitors
that are lemmon yellow pc mounted units, when they go bad
the base of the yellow caps change to a brown color.

I put in the following ECO first but it did not help. If
you look at the service manual you will see that the ECO
values are on the schematic but my unit had the old values.
I suggest that you check the above first, it is a lot easier
to do, C19/C20 can be done in 10-15 min while the ECO will
take about a hour.


2nd SOLUTION: The ECO


ICOM America, INc
2380-116th Ave, N.E.
Bellevue, Washington 98004
206-454-7619


SERVICE BULLETIN


UNIT MODEL R7000
SB# 9288-004
EFFECTIVE DATE 4/1/88
SERIAL # AFFECTED: ALL
PRODUCT GROUP: Amateur

BACKGROUND INFORMATION:
Display failure do to weak components

TECHNICAL INFORMATION:
Improvement in DC to DC converter and display power supply.

PARTS AFFECTED BOARD TYPE CHANGE TO NEW PART NUMBER
Q1/Q2 2SC 1214 DC to DC Board 2SC 2655 906-00385
R1/R2 3.3 KOHM DC to DC Board 5.16 K 915-01173
C3/C4 PF DC to DC Board 0.001 MF 50V 918-01500
ceramic cap
Q11/Q12 Display Board 2SC2655 906-00385
R31/R32 3.3KOHM Display 5.16k Ohm 915-01173
C13/C16 Display 0.001 MF 918-01500

DETAIL PROCEDURE:

1. Remove top and bottom cover.
2. Remove front panel sub-assembly from main chassis of radio
3. Remove the DC to DC board and replace components as listed
4. Reinstall DC to DC board.
5. Replace front panel sub-assembly onto main chassis of radio
6. Replace top and bottom covers.

ESTIMATE TIME TO COMPLETE IS 1 hour

Page 2 of the ECO has a new schematic but no information

--------------end of ECO--------------
 

DaveNF2G

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#10
If I had the equipment to do all of that, I would. The local Icom (commercial) radio shop said they would have to send the R7000 to Icom. Icom has been declining to service their discontinued equipment lately, so I told them not to bother. Besides, the shipping would probably cost more than the repairs.

I think a preamp would be sufficient to overcome the sensitivity loss. I'm not having any of the other problems. If they should appear, then I will scrap the receiver.
 
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#12
Trying to avoid adding more switching power supplies.
And that is why I keep a box of 100 and 200ma 12vdc wall wart power supplies around, antenna related, computer interfaces and modem TNC devices get transformer isolated non switching power supplies, not everything gets hooked up to the Astron RS-70M

Also getting harder to find Icom techs, our local ex Icom tech Kuni retired and is traveling more another Icom and other repair just died and looking at the Icom page do not see Chuck?? and others listed any more. Not many doing board level repair, there are capacitor kits on Ebay. Got 2 R7000s and a R71 that are coming up for them.



David
 
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#13
If I had the equipment to do all of that, I would. The local Icom (commercial) radio shop said they would have to send the R7000 to Icom. Icom has been declining to service their discontinued equipment lately, so I told them not to bother. Besides, the shipping would probably cost more than the repairs.

I think a preamp would be sufficient to overcome the sensitivity loss. I'm not having any of the other problems. If they should appear, then I will scrap the receiver.
You don't need any special test equipment to replace those parts. A DVM might be handy to check voltages and such.
 
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