Vintage amp restoration and Beyond

[GoldenVulture]

I posted this in the mod bug thread.
Some of my pots I ordered arrived today. More to come. I had to order from two different places as neither had all the ones I wanted.

According to the Power amp circuit the O.P.T. primary is 5K. - http://www.ozvalveamps.org/eminar/eminar...uit-sb.png -

Yes I do have a signal generator. I have run the amp in the past but it was very noisy and the slider pots were pretty fucked, That's when I figured I should rebuild it.

I need to go over it and measure all the voltages as they are. I want to get the pots in so there are no stray wires hanging around when I turn it on.

[karpathion]

5k? You should end up with 1k on 4x6l6, and 1.7k with 4x el34s. What tubes did it run originally?

What the hell are you still doing up at 3am? :old:

[GoldenVulture]

5k? You should end up with 1k on 4x6l6, and 1.7k with 4x el34s. What tubes did it run originally?

What the hell are you still doing up at 3am? :old:

EL34's.

 I'm always up till 3 or 4. I rise again between 9 and 10 on average. It's a hangover from my years of living around the R&R/entertainment world. It's a time frame that suits me and I've never had any need to live otherwise.

[GoldenVulture]

The rest of the pots arrived. I'won't be able to get to it till later, other things to do.

[GoldenVulture]

Pots are in. I need to dig up a couple of 6.8K resistors but I'm useless trying to read resistor colour bands by night light, I can't differentiate some colours so they will have to wait till tomorrow. New fuse holder too.








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[GoldenVulture]

Put in the 6.8 k resistors. It turns out I only have two EL's but they went in anyway . That was after I turned it on minus valves and checked a few voltages. A bit out of range. I populated it with valves and turned it on . I had forgotten to check the bias and it started redplating in one valve. I quickly rectified that. It goes but it has a lot of hum/noise and doesn't seem very loud. Wound up it tends to crack up . I missed a ground connection on the second channel and had no vol control but I figured it out and fixed it.

I'm thinking this is all unstable power supply and I need to replace all the caps in it and maybe a few resistors . The same goes for the bias, get a new pot and a few bits.

I did some measurement of the H.T. voltages etc. They're a bit askew . The main H.T. is high and the others are low compared to what the circuit tells me. I'm going to go over it and write it all down. The P.T. is reading higher for the secondary winds than they should be.

[karpathion]

What kind of numbers are you getting?

I have to pull my Windsor/2203 apart again anyways. The presence knob is popping a little, and I forgot the 400v cap change on it. I can check my numbers for a reference. They should at least be somewhat close to each other.

[GoldenVulture]

I haven't done any measurements yet but I noted The plate voltage [ HT1] in this is rated at 648v whereas your windsor is rated at 462v. There are some differences. I'm going to go over the circuits plus the KK mod because I'm figuring the P.T. has plenty to drive a quad of KT88's. I'm thinking if I do a P.S. clean up [ new caps etc ] and it produces the results of eliminated noise, I'll go the whole hog and do the KK mod to run the KT's.
I was trying to do this last night but after a couple of days of wood collecting and cutting etc I was a bit tired and the eyes kept blurring out. I hope to get back to it today plus bit of voltage level measurement.
My Vase runs a pair of 88's and I have two sets. One NOS Gold Lion GEC's and the other is a Gold Lion reissues.
They sound pretty good compared to the GEC's. I'd grab another pair if I did this.

- http://www.ozvalveamps.org/eminar/eminar...uit-sb.png

[karpathion]

Damn, I didn't think they'd be that much different. Yours is definitely going to be more powerful. Kt88s are going to be sick in thing.

[GoldenVulture]

Potentially, yes. I figured I should be able to do the power amp for KT88's and the 2203/Windsor preamp with that weird cathode output.

I've just ordered new caps and resistors for the P.S. I couldn't get an appropriate bias pot from that place so I will have to look else where.

I was looking at the valves when I saw this thing
- http://www.evatco.com.au/product-list/au...-tung-sol/-

KT150 TUNG SOL Matched Pair

KT150 Tung-Sol With a massive plate dissipation of 70 watts, the Tung-Sol KT150 is the most powerful octal beam tetrode ever produced. A pair of KT150’s can allow an amplifier with a power output approaching 300 watts to be built.

The Tung-Sol KT150 glass envelope is a special egg shaped balloon that was developed to improve thermal dissipation and maintain a superior vacuum for the best sound. The fact that the glass envelope has no flat sides means the Tung-Sol KT150 has no problems with microphonics.

KT150 sold in matched pairs only (2 tubes).
$276.90 Incl GST inc. GST

4 in stock

I knew there was a KT120 but now a KT150. FMD. You could make some volume crushing monsters with them.