Aria Pro AG30 tube amp...anyone familiar with

[fredcapo]

I was given an AriaPro3 AG30 all tube amp. It has a pair of 6V6's and two miniature 9 pin tubes which are illegible. Chinese writing everywhere. The transformers in this unit are impressive in size and weight. It appears to be a quality build. Once I replaced the primitive 6V6's which were sparking and flashing, it didnt sound too bad. But i cannot locate any reference to this amp online. Re the 2preamp tubes...how do I determine the type? Measure voltages and try to determine connectivity? If anyone has a schematic or previous exp with this gem please let me know. Thanks.

[Enzo]

Small tubes? First, look at them. I'd bet my lunch money they are just 12AX7, but you can see inside if they are some sort of dual tube. You can look at the wiring, the 6v heater wires will go to pins 4/5 and 9 or they won't. It works, so voltage readings can be assumed to be more or less correct. SO is B+ on pins 1 and 6? Is there a volt or two on 3 and 8? Does touching a small screwdriver or something to pins 2 and 7 make hum come out?

One will be the phase inverter, so the voltages will be different.

The pair of power tubes, you ought to be able to draw up in your sleep, leaving the two small tubes. You should be able to draw up a schematic from the amp from those. With only two tubes for the entire preamp and phase inverter, there isn't room for too many surprises.

[fredcapo]

Enzo

V1 is a 12AX7

V2 is not physically symmetrical as above. I am thinking it could be a pentode/triode PI like a 7199 or 6GH8 from what I see as per pins:

Pins 1&8 send signal via shielded cable to P-P output.
Pins 6&9 are tied together
Pins 4&5 connected to each leg of filament

Thinking perhaps Chinese did not copy a 7199...

Thanks

[Enzo]

Or 6AN8. Sure, pentode triode makes sense too.



Sure, I'd believe 7199, 6AN8 doesn't fit your pin #s.

[fredcapo]

Have been testing the amp in spare time. Not a tone monster but sounds OK with some old usa made tubes. I put meter from safety/green wire ground to the chassis and see 44VAC when amp in standby and fully on. Also on the guitar strings and I think on tip of the input jack. The amp has a polarized 2 prong AC cord. When switched to standby there is a slow bleed off of B+...you get volume for 5 or so seconds, and when power switch is thrown off you get volume surge. I have not probed anything yet. Any idea what may be going on. Sounds like primary issue... Thanks.

[custom_amp_30]

Have been testing the amp in spare time. Not a tone monster but sounds OK with some old usa made tubes. I put meter from safety/green wire ground to the chassis and see 44VAC when amp in standby and fully on. Also on the guitar strings and I think on tip of the input jack. The amp has a polarized 2 prong AC cord. When switched to standby there is a slow bleed off of B+...you get volume for 5 or so seconds, and when power switch is thrown off you get volume surge. I have not probed anything yet. Any idea what may be going on. Sounds like primary issue... Thanks.

Man a gut shot would do wonders as well as pictures of the amp in question. I spent a lot of in Japan and there is a japanese book on Ebay that may help to identify your amp based on it being about Japanese amps only, if its still listed. Good Luck

[g1]

I put meter from safety/green wire ground to the chassis and see 44VAC when amp in standby and fully on. ... The amp has a polarized 2 prong AC cord.

It's either a 3 prong plug with safety ground or it's not. If it's a polarized 2 prong plug then it is not. Do you mean you have your meter to the chassis and the other meter probe to the wall socket ground? Where is the green wire you mentioned? A polarized 2 prong plug does not give you a safety ground.

When switched to standby there is a slow bleed off of B+...you get volume for 5 or so seconds, and when power switch is thrown off you get volume surge.

This may be normal. You are not meant to be playing while the power is being turned off so anything goes.

[fredcapo]

I measure 44VAC between ground of the building/wall outlet and the amp chassis also on strings when power switched on (standby switch either way). The amp is connected to mains via 2 prong polarized plug.

[g1]

You need to change to 3prong plug (with 3 conductor AC cord). The 3rd prong ground should connect to the chassis.

[fredcapo]

Yes of course all older amps should be upgraded with 3 prong. But you have not addressed the issue as to the source of the 44 volts. I don't think it is wise to tie the chassis to ground until the problem is found. I am thinking there must be some live part of the power transformer touching the chassis... Just looking to see if that has happened to anyone on board.

[Jazz P Bass]

Yeah but...
If you are measuring 44 volts from the chassis to 'water pipe ground' it is more than likely the death cap.
True there is a voltage but is it capable of sustaining a current?
Probably not.
Remove the death cap & then take a voltage reading.

[fredcapo]

OK thanks...that's the guidance I was seeking...no schematic but will find it. Thanks to all.

[g1]

The voltage you are reading may just be a "ghost" voltage because the chassis is not grounded. Sorry for being vague about it.
If this is the case, it may not be capable of delivering current, as JazzP mentioned.
You could try connecting a resistor (100K for example) in series between the chassis and the wall outlet ground. If the voltage disappears, it was just because the chassis was floating and is now grounded.
If the voltage remains with the chassis grounded through a resistor, then there is some other fault, such as the "death cap" being leaky.
Either way, when you change it to 3 prong, the death cap should be removed.

[TomCarlos]

An old thread, but look what I found... an Aria-AG30V amp. If you look at the back, is shows "Arai&Co."

The amp works. But I would like to try out a pair of 6V6 tubes in place of the 6P6P.

V1 appears to be a 6N4J. I believe a 12ax7 should work.

V2 is the unknown. As stated previously, the pin outs appear different compared to V1. So the question is... do we have a 6AN8, or some other tube there. I am checking to see if it can be a 7199 as reported earlier. The tube in V2 is 9 pins. If possible, I would like to swap out V2 for a modern day easy to find tube.

This will not be a gigging amp. But it would be nice to have something cheap to test out preamp tubes or 6V6 tubes.

Finding the schematic has been next to impossible. But I will keep looking and report back when I do some testing.

[TomCarlos]

Update....

I dropped a 12ax7 into V1 - amp works fine.

I had to go full counter clockwise on VR4 to increase the negative voltage on the Power Tube grids. I am now running 6V6 tubes, 330 volts, 27ma. So that puts us at 65% dissipation.

I think we can rule out the 6AN8 tube.

The socket is wired up where Pins 4 and 5 see 6.3vac (filament). I then see a short wired between pins 6 and 9. So no way that can be a 6AN8. On that tube, pin 6 is a plate and pin 9 is the corresponding cathode.

This phase inverter is looking similar to a Long Tail pair.

Pin 1 on the socket has 236 volts and has a coax cable most likely heading towards the output tube.
Pin 8 has 90 volts and also has a has a coax cable most likely heading towards the output tube.
Pin 2 has -.12 volts - most likely a Grid?
Pin 3 has 54 volts - Can this be a Cathode?
Pins 4 and 5 are the heaters and have 6.3vac between them.
Pin 6 is connected to pin 9.
Pin 7 has .872 volts - most likely a cathode?
So where is the Grid on the one side of the resistor?

So the search for the mystery tube continues. I am checking to see if the v2 tube is a 7199 - the pin outs could match up.