FT225RD, FT902 repair

Old rigs of s.k. Eltje PA3CEE  here for check and repair
The rig's looked like they have been working in a brown cafe for years
He was a real smoker ...

the "tank"  FT902DM  very heavy rig

permeability tuning  very well build equipment. Plug-in modules. 

The standard twin 6146 PA seen in most most older transceivers until 30 years or so ago
shown under power with filaments on.
Dangerous be aware ! 950V  and 350V are also present at the ACC  backside socket for external use 
In the age of SSPA used to low voltages where  touching a working circuit is safe.
Working with high voltages is extra dangerous nowadays.

The socket board of the PA the brown C looks high-quality is a known issue of the FT902. This 100pf /1kV is to separate 350V  12BY7 driver ANODE  from the delicate  6146 grids -100 150 !  practical a wire direct from the driver anode is leadingto this C1   If shorted the PA wil blow the fuse shortly after the heaters are switched in  .. if lucky fast enough to prevent destroying the tubes. If C1 fails in full operation the tubes can explode what at least happened to 1 tube here. It is advised to replace  C1 premature in all FT900 sets. The value 100pf is a trade off between between the lowest band 1.8Mhz and 28MHz if a higher value is chosen the grid tuning is affected.

The  100pf 1000V mica capacitor was shorted and caused the 6146 damage one tube glas was busted
I replaced both tubes ... warning be very careful not to touch the anode part  almost 1000V stays long time loaded in the HV high capacity capacitors, no bleeder R it seems.
Before doing any work make sure the anode C is unloaded I used  a 10k resistor against ground with an isolated gripper and grounded wire!



----------------- the other rig 144 - 146 MHz all mode --------------------------------

FT225RD    20-25W rf

The original  front end was replaced by a Mutek front as that was often done 30 year ago.
However my  FT221R  the preceding   have the original front-end ,i can't find this one less performing.  And the FT221 can handle the extreme strong local contest station PA1T . That is about the strongest signal on the band.
It is not like in the glory days of 144MHz activity 30years ago  when this FT225 was state of the art.

The FT221R is taking very low standby power less then 300mA at 13.5V Not using the internal power supply since that is getting very hot in long FM QSO
Unfortunate The FT221 / 225 have no PC interface it is also not stable enough for WSPR  / FT8 modes.
One FT225/215 issue is bad contact in the switches. It was hard to switch modes in this FT225  loud cracking in the speaker but simply a few drops of  ordinary spiritus  upon the outside of the  switches  completely smooth and quiet now.

My IC706 that is not much younger but still technically up to date
Receiving 144MHz cw /usb signals is a pleasure on the old rigs with almost zero ground noise . Most SDR rigs bring among a lot of extras also a high internal noise level.
No matter  how well the DSP filters function this noise wil stay.

No CTCSS sub carrier for repeater option but it has a Tone burst unit  that generates 1750Hz
when pressing burst button , that will not work for repeaters using CTCSS lock
I use a small pcb based upon Attiny85 that can generate 4 selectable  designed by PE1JVU
His software uses Pwm  output this makes a reasonable clean sinus signal with a simple RC filter
An other CTCSS using a pic controller i use outputs a square wave difficult to make a sinus shape with  a simple RC filter  and therefore have hum overtone issues

ft225 card-edge are very good accessible to find an ctcss injection point close to the varicap modulator
The FM mode modulation level can be monitored at J22 B14 I keeped the ctcss level way below the normal microphone level. No hum issue at simplex although the ctcss tone is always in FM tx .Not found a FM shift tx voltage.

the Attiny is programmed with the bin file using Ponyprog, i had an issue when setting the fuses CLK3-0 1111 as noted in the program source the Attiny was "bricked"  Needed the reset the fuses to default with an rescue Uno sending 12V "highvoltage" pulses to the Attiny reset.
https://sites.google.com/site/wayneholder/attiny-fuse-reset 

These are the fuse settings in Ponyprog security bits setting that give  correct CTCSS tones using the external 10MHz xtal
the default fuse setting does use the internal clock reference causing a 20% too low freq out.

-------------------------------------------------------
Last weekend was the May IARU VHF/UHF contest.
Everything is completely different in the Corona virus lock down
So PI4GN multy band/operator operation was no possible! who could imagine this in the last March contest!
Now i should do the 23cm part from home
My modest 23cm is a 1.2m dish with transverter direct on it  35W out
Rx the latest SKY67150 LNA  0.4 n.f measured claimed 0.3 n.f. bandpass filter included.

What to expect when most big contest clubs are forced QRT and  tropo is very poor
more home stations i hoped for..
Saturday morning i had to replace a control cable connector due in-watering

But the 23 band was empty very quiet the normal in-range beacons all very weak .
It was was hard  to find QSO partners a QSO was rare..
Only Airplane scatter could be used .
Installed latest Airscout version the old one showed no planes.
Then Sunday 4 hours before end sudden no more RF power
something wrong receiving was still okay
Premature end of this remarkable weird contest forced with only 22 contacts
worst ever March was also poor tropo but then our club station was operating and  others in EU
70cm could bring 23 skeds
then we had 65 Q average over 400km .

things can change quick