Advent 300's in the House

[Lazarus Short]

I have 4 extra , how many ya want?? There is a dark arrow or black slash with a directional arrow pointing to THE NEGATIVE lead.

What brand are they? I'll need two, as I'm probably not going to fix up both of them. I'm almost afraid to crack the dead unit and see what the guy did...but I'll have to do it sooner or later. The working unit was assembled in Mexico (a late unit) and the dead unit was made in Massachusetts. If the board is buggered up and if it's basically breadboard, I can probably rewire the volume control using the other unit as a guide. The way it's put together, I think it will be easy to work on, and the more I look at it, the more I think it looks like a cottage industry unit.

Anyway, if you'd be so kind as to send me a pair of caps, I'll at least pay the shipping.

 

[laatsch55]

Sorry Laz, 4 extra 2000 Ser II's.

 

[laatsch55]

What voltage are they??

 

[Lazarus Short]

30 VDC

 

[laatsch55]

Shoukld not be hard to find. I use Mouser and Digi-Key....

 

[Lazarus Short]

OK, I'm settled on a pair of audio-grade caps from ebay. Now, a question on the other end of the signal chain - I looked at the power transistors again, and they, six of them, are mounted on top of what looks like thin sheets of plastic, which are looking the worse for wear. I'm considering the probable need of applying new heat-sink compound, but am I going to have to scrounge for some mica gaskets? Any ideas??

 

[laatsch55]

What style of outputs? TO-3, TO-220, TO-264?.....

 

[Lazarus Short]

I replaced the power supply filter caps tonight, was swinging past Radio Shack earlier, and wondered...? There they were, 4700 mfd, 35 vdc, two of 'em, axials too. Nichicons, and smaller than the original Mallorys. I fired it up cued the music, and...the right channel sounds great, left channel no sound. It comes in with the headphones, so I'm going to clean the pots tomorrow. Wish me luck. Photos below. It looks like the "Assembled in Mexico" unit will be the keeper, as I keep seeing that it is better, even besides the broken volume pot in the other one. The output transistors are mated to the heatsinks with proper mica, not the cheesy plastic in the Massachusetts unit.

BTW, Laatsch, you got FOUR series II 2000 preamps just sitting around? I had one, loved it, stupidly traded it, miss it. Best, and cheapest preamp I ever owned. Aargh!

 

[laatsch55]

Yes I do Laz. Actually I think there are 5 series 1 and 2's. 2-3000 Ser II's, 1 3300 Ser II. The one 2000 Ser II is a pretty nice unit. Need to recap and replace the op amps and it would be stellar, or buy it like it is for 180.00

 

[laatsch55]

Nice job on the cap replacement/.

 

[Lazarus Short]

Nice job on the cap replacement/.

Thank you, it really wasn't hard, once I got roun'tuit. The right channel is very nice, and has good tonality, but the left channel is still zip, after cleaning the volume pots. Then I remembered something the fellow (who sold it to me) said, that he disabled the tone controls. I took off the bottom cover, looked around the traces near the balance/bass/treble pots, and there they were, eight de-soldered holes around the "Bass" pot. He took out some caps, so the next step will be to put the two 300's side-by-side and see what is missing. I'm not entirely sure my soldering skills will be up to this, but I'm determined to fix this thing myself, if i can. My big worry is that the two circuits are different revisions. More later...

 

[laatsch55]

Yeah the "Revision" thing can bring a screeching halt to a comparison replacement.

 

[Lazarus Short]

Success!!!!!!!!!!!!!!!!!!!!!!!!!!!

Well, sort of...

I decided to do the circuit board comparison tonight, but only found the same holes on the Massachusetts unit (the old one with a broken, no, call that busted, volume control). Then, the light went on. Here I had in front of me, two receivers, both with pre-outs, and power-ins. Um, that might work. I set it up for the Mexican unit to serve as the preamp, and the Massachusetts unit to be the power amp. Connected speakers, source, and patch cords...pressed the "play" button. Music! Both channels!! Thank you all, especially Laatsch, for all the help and advise.

 

[laatsch55]

Cheerleader was more like it.

 

[Lazarus Short]

Well, I may have crowed "SUCCESS!" too soon. Given the iffy interconnect connections (maybe I should call them inter-not-connections), I worked on the contact surfaces with CLR, a product similar to Lime-Away. I used the rolled-paper sticks from a couple of lollipops, as they were just the right diameter. I could just see the dross and corrosion melt away. When I was done, I could see bright metal in the inside-pin surfaces, and some brassing on the outside.

When it was all done, I was able to see which channel worked and what didn't. I ended up using my best patch cords (British Cable Talk) to connect L & R preamp out from the top (Mexican) unit, and R power amp in on both units. With this arrangement, I can't even think of using my balance control, a minor downside. I'm yet going to try the left channel of the Massachusetts unit. One of these days, I'll get the Mex unit fixed properly, but this stopgap will help me decide if I did the right thing in buying these in the first place.

 

[laatsch55]

Interesting stuff

 

[Bob Boyer]

I know this thread is more about repairs to the 300, but a little history on the unit: the real interest in the receiver is the phono circuit. Harry Pearson, in one of his earliest issues of The Absolute Sound back in the 70s, was extolling the use of the Advent as a preamp based on the quality of the phono circuit Thomlinson Holman, who went on to found APT/Holman and produced a couple of pretty nice preamps, was the designer for the Advent 300.

It holds up well to this day as either a receiver or preamp, but probably better as a preamp.

 

[Elite-ist]

Interesting facts, Bob. I don't know much about the Advent 300, but once a thread like this appears, I make a mental note of it. Nicely repaired, Laz!

Nando.

 

[Lazarus Short]

Actually, not repained, nicely or otherwise - both units are put away and I'm using the excellent phono section of my Arcam Delta 60. Buying the Advents was a mistake.

 

[Elite-ist]

Actually, not repained, nicely or otherwise - both units are put away and I'm using the excellent phono section of my Arcam Delta 60. Buying the Advents was a mistake.

Usually, the "to-fix" pile is doomed to storage for a long time. Perhaps, one of Lee's PL2000s would be a future addition?

Nando.