Triode Bias board (Erratic GS35b)

After having serious Amplifier problems I finaly found out my tube was glitching so every now and then.. My PA is in a remote room, I used it in this set up for years and years. Just tuned it once and no worries about the PA just switch it on and operate. But a few months ago I had a small failure it looked like the HT fuse was blown by accident, also the mains fuse was broken and PA was without cooling after that as the fan wasn't running anymore. The Anode couldn't radiate it's heat.. After fixing the fuses all worked again. Same output power but now more often the HT fuse went QRT without (pre)notice. I suspected the Bias circuit as it was just 2 transistors some resistors and a potmeter. so I rebuilded the Bias circuit with a TL-431A regulator and a TIP-147 darlington PNP transistor. Aligned it at 40V for 150mA bias current. All was working fine again.. After 30min of standby I wanted to transmit but NO HT.. All was left which could cause the problem was the tube.. I had a spare tube which has been in my amp for years, I installed the tube in the Amp tuned it and got full output again. Today used it for an hour, left it on standby for 2 hours. It doen't run warm anymore and no glitches. So the old Tube is RIP.. Took a hammer to have a look inside, very clearly you can see there has been some arcing IN the tube between Grid and Kathode. See pictures below. On the first picture you can clearly see the Arc between 37 en 45 minutes (in the 6th 1/8 part of the pie)


The Grid and Kathode (not exactly in the centre) Russian precission


The bias circuit 


The Anode.. Tube has been heavily (ab)used 

New PCB designed and ready for shipment : 

I can supply bare boards, or kits

Size of the board is 31 x 43 mm with 4x 3mm mounting holes

A Heatsink is NOT included. 


Bare board + documentation 7,00 Euro  including shipping worldwide
Each extra board 6,00

Complete kit = PCB + all needed components 17 Euro including shipping worldwide
Each extra kit 15 Euro

Email me for info or larger quantities.

Shipping via letter airmail in a bubble enveloppe.

There is enough stock again..


REMARK the new boards are BLUE not RED as in the picture, they are electricaly equal. The supplied TIP147 is as in the upper picture (right angle isolated)







Reacties

  1. mangiavo sul ponte28 juli 2020 om 03:19

    Good morning John
    i was looking around for a easy build triode board and i found, on ebay, your board.
    Im bulding a "small" qro with 2x GI7B.
    Can I use two of your board for this amp?

    thanks for any suggest

    73

    Gabriele IZ5FCC

    BeantwoordenVerwijderen
    Reacties
    1. John Peters18 augustus 2020 om 00:37

      Sorry for late reaction, but 1 board is suficcient for 2x GI7b

      73! John PA5MS

      Verwijderen

Een reactie posten

Populaire posts van deze blog

Elevation system

Afbeelding
To put up my 4x11 el F9FT's I was in need for a decent Elevation system. In my old system I (ab)used a KR500 but thet rotor did not last very long and was not able to elevate over 60deg due to the weight of the antennas. I build A new system with a 12 inch satellite actuator. It's still in the backyard on a small pole just for testing purposes. Welding is not my thing but I managed to get it solid fixed together.. Not bad for an Electrician I must ommit.. Building up the tower, Elevation system mounted on the 60mm steel pipe 3mm wall thikness. Antennes in full glory..
Meer lezen

Ecoflex 15 don't bend it too much..

Afbeelding
Hi After having found SWR problems and erratic behaviour of my amplifier at high power levels I started checking the whole antenna system. First I found after calculation that my powersplitter was not exact 50 ohms but "only" 48 ohm. Resulting that it transforms the exact 50 ohm antennas to 46 ohm.. so a mismatch. I build a new splitter with exactly the right dimensions Outer conductor square 32mm inside diameter and inner conductor round 15mm outside diameter. This results in exact 50 ohm. After replacing it, I terminated it with 4x 50ohm 10W terminators, applied power to it and found a good SWR, but not flat over a large part of the spectrum. On 142 MHz impedance was only 35 Ohm while on 144 it was exact 50 ohm, then on 149MHz another peak. This told me that there is some impedance mismatch in the cable. The first 35m is 7/8 cellflex.. After terminating that piece with 50 ohm SWR was flat form 120 to 160 MHz so it must be the last part of the cable 15m Ecoflex-15 from h
Meer lezen