Pilot PT-1030 B?

[BmWr75]

I saw one of these monophonic consoles at a junk store today. It contained a mono TT, preamp and amp. Anybody familiar with this model? I didn't get it since it was mono, but could make another trip if it would be a worthwhile restore. Sorry I didn't get any pictures, my phone battery died on me while I was out.

EDIT - added some pictures I found in the web.

 

[Tinkerbelle]

That is some beefy OPT and I would bet produces sweet music to rival the better Fisher & Scott 6BQ5 amps. You might have to wait a while to find a mate... however... if I am not mistaken, that is the console version of the AA-903B (not AA-903) - there is one up for auction if you want to x-check on similarity.

 

[BmWr75]

It is an integrated amp, can see that now after looking at the first pic in the first post. Pilot made some good stuff. The SA-232 amp I have is on the never sell list.

 

[gadget73]

Indeed, Pilot did make nice stuff. If you do get it and gut the console, I could really use that lid stay. My console uses one just like that, and I have not had much luck finding one. Changer looks like an RC88/4, which isn't especially amazing but would do quite fine as a 78 machine if you're into that. Looks like its got a GE VR-II on it as well, which is a right decent mono cartridge as I understand it.

 

[BmWr75]

I went back and picked it up today. Here are some pictures.

Pulled and tested the tubes, they all tested good. 2 Mullard 12AX7s, 1 Amperex 12AX7, 2 Amperex EL84s, 1 Amperex 6CA4

 

[Dswankey]

Very nice!!!!

 

[BmWr75]

Decided to restore it. Have already inventoried the caps. Need to see which ones I have on hand.

Anybody got a schematic?

 

[BmWr75]

More pictures

There are wires going to the front of the woofer, see the picture. They are at about 3 and 9 o'clock. Coaxial driver?

There is another driver enclosed in the wooden box just out of frame on the right.

 

[gadget73]

Good deal, you got the single play and 45 spindles for the RC88 as well. Those parts are very often lost.


Not much of a reason other than a center tweeter to have wires feeding into the speaker like that. The 4 into the base are curious though. Is that a field coil speaker ?

 

[BmWr75]

I need to see where those wires through the bottom of the cabinet go. Have not looked at the bottom yet since it is on caster and is easy to roll around.

 

[BmWr75]

One of the cap cans, a paper covered one, contains a 250 uF 35V and 500 uF 35V paralleled together to total 750 uF. I've never seen caps cans with that high a uF on a tube amp. Am I ready the cap can lettering correctly.

 

[Tinkerbelle]

Decided to restore it. Have already inventoried the caps. Need to see which ones I have on hand.

Anybody got a schematic?

I think I have the Pilot AA-903B schematic

 

[Tinkerbelle]

One of the cap cans, a paper covered one, contains a 250 uF 35V and 500 uF 35V paralleled together to total 750 uF. I've never seen caps cans with that high a uF on a tube amp. Am I ready the cap can lettering correctly.

It's not unusual to have high µF low voltage caps for the bias supply.

 

[Tinkerbelle]

Schematic for the AA-903B is here and, yes, it has a 750µF 35V cap: http://www.acousticpsychos.com/Files/Pilot/pilotaa903b1.jpg

 

[BmWr75]

Thanks much @Tinkerbelle.

 

[BmWr75]

So I am guessing the selenium rectifier needs to be replaced with something more reliable. At least they do on Dynacos. Any thoughts on what to replace it with?

 

[gadget73]

Silicon diodes with a resistor to drop the voltage down somewhat ought to do it. A 1N4007 or UF4007 should be fine. Not sure on the resistor, maybe try 10 ohms and see if it comes out OK. Might have to bump that up a bit, but my guess is 10-20 ohms will do it. I'd hang a cap on each end of the resistor too. That should actually give somewhat improved filtering vs just a single big filter cap and no dropping resistor, or a resistor with no cap. If you want to be nice to the diodes, put a larger cap after the resistor and the smaller one right after the diode. That would help reduce inrush current.

 

[BmWr75]

What wattage should that 10 ohm be? I'll measure the voltage to adjust the resistor size, but need an idea on wattage.

EDIT - Looks like a 5 watt will do.

 

[BmWr75]

I think the three 12ax7 heaters in this are wired in series. Will double check that later. But, if they are, each heater needs 12.6 VDC and draws .15 amps per the spec sheet. The schematic says the PT puts out 16 VAC, but I measured it at 17.2 VAC. So, the voltage drop across the new diodes and resistor needs to be 17.2 – 12.6 = 4.6 V. Ohm’s law says I need a 31 ohm resistor. Will do some experimentation with 10, 20 and 30 ohm resistors and see how the new diode pair and resistor works out.

If anyone sees any flaws in this logic, please speak up.

 

[BmWr75]

Not much of a reason other than a center tweeter to have wires feeding into the speaker like that. The 4 into the base are curious though. Is that a field coil speaker ?

Even though it looks like one from the back, don't think it is. I've got the amp out on the bench working on it. So, there is no power in the cabinet and the woofer still played today when I rigged up a T-amp and iPod.

I can see through the cloth that there are two tweeters mounted on a frame in front of the woofer. The mid-range is mounted in a wooden box that has front port slits on it. Was surprised how decent the speakers sounded on things that aren't bass heavy.

Somebody asked about the two wires going through the base of the cabinet. They go to a G.E. 1847 pilot lamp that is mounted under the cabinet and covered with an opaque black paper tube. Strange.........