Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: LooseChange on March 02, 2011, 10:22:24 am

Title: Airline Reverb Unit schematic??
Post by: LooseChange on March 02, 2011, 10:22:24 am: Got one of these on the bench... Distorts but sounds cool.
Anyone have a schematic?
Thanks!
Title: Re: Airline Reverb Unit schematic??
Post by: LooseChange on March 03, 2011, 05:09:56 am: It's the stand alone unit.
Has a 5Y3, 6EU7 and a 6DR7. Never seen a 6DR7 before.
Thanks!
Title: Re: Airline Reverb Unit schematic??
Post by: kagliostro on March 03, 2011, 05:28:11 am: I had a long search for your airline schematic

the only airline schematic I've seen are radio schematics

may be if you have a name or a number for that unit it will help the search

Kagliostro
Title: Re: Airline Reverb Unit schematic??
Post by: LooseChange on March 03, 2011, 07:57:06 am: Thanks for looking Kagliostro.

Just found the model number under the rust... 62-9019
Thanks!
Title: Re: Airline Reverb Unit schematic??
Post by: kagliostro on March 03, 2011, 12:05:17 pm: Sorry only some photos but no schematics avaiable

Kagliostro
Title: Re: Airline Reverb Unit schematic??
Post by: VMS on March 03, 2011, 12:42:01 pm: I found a schem for gvc-9019a:

http://www.webphix.com/schematic%20heaven/www.schematicheaven.com/bargainbin/airline_wards_gvc-9019a.pdf (http://www.webphix.com/schematic%20heaven/www.schematicheaven.com/bargainbin/airline_wards_gvc-9019a.pdf)

Does that look similar to what you have on the bench?

This bargainbin has also other airline schematics:

http://www.webphix.com/schematic%20heaven/www.schematicheaven.com/bargainbin.html (http://www.webphix.com/schematic%20heaven/www.schematicheaven.com/bargainbin.html)
Title: Re: Airline Reverb Unit schematic??
Post by: kagliostro on March 03, 2011, 01:40:38 pm: Number 62 was a suffix used also in other apparatus like radios

I think that the gvc may be the right schematic, also if from the photo I've seen is not possible to establish if the layout is the same

Kagliostro
Title: Re: Airline Reverb Unit schematic??
Post by: LooseChange on March 03, 2011, 02:08:33 pm: Thats it! Thank you!
Now I need to figure out if the distortion is how it's supposed to sound.
Title: Re: Airline Reverb Unit schematic??
Post by: PRR on March 04, 2011, 11:23:04 pm: > if the distortion is how it's supposed to sound.

Straight or reverb side? Both?

Basic voltage checks.

What is the raw B+, and does it drop "some" going down the filter chain?

The first and third stages are simple voltage-gain stages. You expect the grids at dead-zero, cathodes to be at a few volts, plates at 1/2 to 2/3 of that stage's supply voltage.

The second stage is another voltage-amp, except with a VERY fat triode, high current. (More like the 6V6 in a Champ than a 12AX7 stage.) Expect the cathode at about 5% of supply, plate at 1/3 to 2/3 of supply.

R-11 is 10W so could work with 223V across it, 150V would be better practice, 100V would not justify a 10W part in a cheap amp, it would be 5W. Some pondering of the 6DR7 specs say it and its cathode resistor drop a little less than half the total supply here. So the total supply at C-13 must be over 200V and under 400V, probably 300V. The big-triode current is 30mA-40mA, other stages a mA or so each. Taking 40mA in R-25 R-26 gives C-14 voltage 40V higher than C-13 voltage. So the raw B+ at C-14 is probably 320V-375V area.

The fourth stage is a self-bias cathode follower. Really a volt-amp but with the 100K moved from the plate to the cathode, upside-down. So expect the 100K at 1/3 of supply, the cathode a couple volts higher. _Any_ leakage in C-9 will slam the grid and cathode to ground.

Stray thought: R-1 R2 470K is awful high. Keeps radio out, but kills a bit of treble. I wonder if it is a typo for 47K. A couple 68K here works well for Fender and many clones.