Skip to main content

IC706 classic repair

IC706 classic  was damaged by high RF at 144 input
I use this old but very good rig as 146-148  i.f for 1296MHz  XVTR
Receiving Graves at 143.050  pings and scatter i forgot to disconnect the VHF antenna   ( 3 band 6,4,2) when transmitting at 6m with the 7 el just underneath so it became very quiet at 23 / 144..
144-148 /VHF input circuit part with 3-PIN antenna switch  and MA862 band switch that switches between 2 input filters. TOP = 60-200 MHz  down is 144-148 bandpass
preselection in front of the    uPC1658G  wide band preamp



MA862  bandswitch fried by high 50MHz signal at 144 /VHF input SO239


replaced by 2 BA891 bandswitch diodes Ebay 



above temporary jumper to select 144-148 band pass filter
without the bandswitch diodes the IC706 does not switch to the VHF filter when tuning outside the 144-148 range  a solution without bandswitch
But the burned out  MA862 protected the IC706 preamp against further serious damage
So it is better to have  bandswitch diodes placed there
4 pole tuner connection covering 144 input circuit removed , i needed to file off the sharp edges of the HF PA input transformer LR322B 
The MA862 is dual diode SMD  band switch
< 0.7 OHM    Cd  1pF or less
this hard to get part can be replaced by 2 BA591,135
having same specs


btw  finally decent pictures again the 2 pictures above are token
with a new Huawei P10 lite replacing HTC with broken  camera
 besides the excellent camera the P10 is much faster
Unlock easy with fingerprint scanner at the back
i do advice the smart view cover for protection
And do not take this phone with you to Barcelona if you want to keep it...

Comments

Popular posts from this blog

SPF5189z Low noise preamp 23cm

14-4-2018 updated


Above the low noise  preamp 50 - 4GHz    ebay  6€

Tested  2 small porto antennas
1 Baofeng UV antenna left   2nd best signal on PI2NOS
2 eBay DIAMONDSRH805S  wide band 144/432/1200  it works for its size as expected
3 piece of wire :   best signal in the setup...

Unit under test at workbench.
It was stable  50mA  at 5V   few days,  but sudden the current went up to 100mA
And i could  no longer adjust it with the negative bias Voltage.
The - Voltage went to zero and the SPF input port became low Z.
This SPF5189z was broken  no oscillations, no input overload just it broke while i was receiving the PI2NOS 430.125 using a small antenna at the workbench.

The specs of  SPF5189z  say it has an internal circuit  regulating the bias current.
Replaced . again   with an other of the 5 spare SPF i have.
The new one again could be adjusted at 50mA  5V 
The current raises to 150mA  when removing the  negative gate voltage.
Where is that internal bias circuit ?
I suspect  eBay …

2011-01-22 DIAMOND X30 2m 70cm 1m30 Colinear inside

Having relative poor signals on the local 70cm / 2m channels using this Diamond collinear 70/2 combi antenna at a height of 25m. I needed to investigate what could be wrong.
Measuring the cable only 3W is left for the antenna of the 10W 435MHz output from a IC451E
The cable is 30m type H100 Z50 10mm outside diameter it is semi air-spaced but has an impossible 4mm² solid CU inner conductor not much air left. I preferred the H43 Z75 cable having lower loss and mechanical better ratio in conductor size but it is no longer selling i think. This H43
3W should be enough for a comfortable noise free FM signal. But only 27km away at PA0A the signal is weak too weak something must be wrong? I made a simple reference dipole of 2x17cm CU wire.
With this dipole the signals where totally worse. So the Diamond does work?
I got curious to look inside. Maybe moisture penetration degraded the antenna.
This  antenna is rainwater close in its normal vertical mounting position. But take care if your mast can b…

Nice opening10m and 12m to S.A.

SFI  low 70 a 16 K3  still 10m opened up in afternoon to N-Italy EA5 F JN33
F/PD0OHW/M in JN33 decoded 150mW

VP8LP  12m    2-way with GP 7m ag swr 1:3


60m 5,362 open to ZL every? morning