Skip to main content

60m and Tektronix 465 in trouble

474.2 of for the 1 rst time in weeks no decodes of AA1A
 high bands still very good   10m VK2KRR      HS YB C9 ZS CE ZP CX PY stiil many

hrd and called 80 HS YB JA not all JA could cpy
then suddenly later in night all DX gone

atn   DU1GM    en 6Y4AT

T2AR    60m hrd JT65 very weak 2 decodes -20 -22  early morning longpath ( only possible i think)
TUVALU   in  RI99ol  exotic grid..

Call signWorkedDate/TimeBandModeFreqQSL
DetailsPA0OW8WDR2017-10-26 05:36:4580MFT83.57354
DetailsPA0OW4RIX2017-10-26 05:22:3080MFT83.57354UNITED STATES OF AMERICA
DetailsPA0OW1PFZ2017-10-26 05:17:1580MFT83.57354
DetailsPA0ON3OUC2017-10-26 05:05:1580MFT83.57354
DetailsPA0OHP1XT2017-10-26 05:02:0080MFT83.57354PANAMA
DetailsPA0OWS5W2017-10-26 04:57:3080MFT83.57354UNITED STATES OF AMERICA
DetailsPA0OWF1H2017-10-26 00:07:30160MFT81.84041UNITED STATES OF AMERICA
DetailsPA0OKX4TT2017-10-25 23:59:15160MFT81.84041UNITED STATES OF AMERICA
DetailsPA0OW1TC2017-10-25 23:57:45160MFT81.84041UNITED STATES OF AMERICA
DetailsPA0OI1BEP2017-10-25 23:47:15160MFT81.84041
DetailsPA0O6Y4T2017-10-25 23:33:3060MFT85.35741
DetailsPA0OEY8MM2017-10-25 23:24:0060MFT85.35741
DetailsPA0ODU1GM2017-10-25 20:13:0060MFT85.35741
DetailsPA0OKE7B2017-10-25 20:00:0030MFT810.13641UNITED STATES OF AMERICA
DetailsPA0ODL1HDL2017-10-25 19:12:4580MFT83.57341
DetailsPA0OVU2ABS2017-10-25 19:05:1580MFT83.57341INDIA
DetailsPA0OK1IED2017-10-25 18:38:0017MFT818.10041
DetailsPA0OKK4LH2017-10-25 18:26:3017MFT818.10041
DetailsPA0OW4HHN2017-10-24 23:35:00160MFT81.84041UNITED STATES OF AMERICA
DetailsPA0ON3GAR2017-10-24 23:19:4560MFT85.35741UNITED STATES OF AMERICA
DetailsPA0OW4HHN2017-10-24 23:16:1560MFT85.35741UNITED STATES OF AMERICA
DetailsPA0OK8MFO2017-10-24 23:12:3060MFT85.35741UNITED STATES OF AMERICA
DetailsPA0ONE1I2017-10-24 23:03:15160MFT81.84041UNITED STATES OF AMERICA
DetailsPA0ON4ULE2017-10-24 17:40:0012MFT824.91541UNITED STATES OF AMERICA
DetailsPA0OKF4BI2017-10-24 17:35:1512MFT824.91541UNITED STATES OF AMERICA

  oops this part should be separated but  it melted together in html

equipment in trouble
My Tektronix  465  after 30 years +  service sudden the CRT trace was gone
The fault had to be in the in the CRT H-Voltage part.
The Tektronix 465 is a real electronic masterpiece
 amazing advanced equipment from last century  70 ties
It is service friendly most transistors are in sockets.  And documentation is still available at Tektronix.

But the H-voltage sm-transformer and cascade are  most difficult to get to.
Laying in a shielded box under the V-amplifier board.
This bord has to be removed  the front panel was removed with all of its buttons.
Youtube shows remarkable examples how to refurbish or repair the 465 scope.
But removing the board and front is not shown. This is a real challenge i do not want to give up on this scope.
Special SAE hex-key's  are needed , preferable long shaft  T-shaped  models the hex bolts are very fixed.

I had to study a bit the SAE tool dimensions

4/64  = 1/16 for most buttons, 5/64 for the time div switch shaft
3/64   for the dial and  the  trigger view push 20MHz pull shaft.

The 4 internal nuts  that fix the board at the front   an 1/4  with a flexible shaft can just do it .
I believe the 465 needs customized tools high quality  Chr-Vanadium steel.
I managed to modify metrix Hex key with a diamant  sharpener
the hard way that worked for almost all knobs

Found a local hardware shop that sells SAE hex keys of good quality.
De Koning
Nieuwe Ebbingestraat 26
050 3125953

It will have to be a DIY  6x Cascade like this one, since reasonable prized replacements are hard to find
Cascades are like in the old days of CRT TV a weak spot of Oscilloscopes if there are any available they are sold quick. 

                                                                 still some more knobs to go

                                            deep under the board and FAN motor is the suspect HV unit

Finally the Vertical amplifier board  was removed.
The input C's  3 legs!  have to be un-soldered to unscrew  the 4 nuts backside front panel.
Complicated job  these coupling C shields are soldered to ground hard  to see.
Removed the front cover plate and all !  knobs hoping to find screws that hold the V-amp board.
That would make this job a lot easier..
But no screws the wire ends are fixed to the frame  i should have read section 4-9 first
The Front cover plate was removed for good cleaning anyway.

 page 4-9  does not tell you all  nasty details.

Additional 3 extra wires and  a ground wire need un-soldering.
Removed the CRT socket for safety  for if the Voltage regulation would be way to high.
After separating the HV multiplier cascade
Yes! the 2450V  was back and the voltage regulating looks fine.
Then i  plugged the CRT socket back on.
 ! Warning  !  do not try to  measure the heather voltage with a non floating meter since the cathode is -2450v to ground!  A standard 50Hz  meter can not measure the 50kHz AC anyway

I measured  safe at the collector Q1418  30V tt  about 66kHz sinus shape.
Bit higher then should be 50kHz without the load of the 14kV-cascade.
A short time after boot  a beam dot was visible until the build  h-V in the CRT vacuum leaked away.
So the Cascade really is the problem as I had suspected.
Very hard to replace , it would not lift up enough to get the wire studs complete out.
And the HV  connector was struck under the CRT shield the part  doesn't want to leave the 465..
I seems the whole 465 has to be disassembled to replace a broken cascade

The 465 is a masterpiece of electronics but there are some weak spots.
Now the 465 disassembled parts are resting in boxes waiting  for a cascade possible a DIY type.
 6x 1nF 6kV 6x 10kV fast recovery diodes
the parts are ordered from Ebay

Radio market's  do not sell 10kV diodes   and the C's sold  5x more expensive
 no wonder that most HAM's  purchase their parts online.


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