Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => The Newcomer's Forum => Topic started by: Scoticus on January 24, 2017, 11:50:04 PM

Title: Yamaha G100-115 II reverb tank
Post by: Scoticus on January 24, 2017, 11:50:04 PM
Hello all
just scored a G100-115 series two
does anyone know what reverb tank It should have ?
the bag is still there but no tank.


Anybody own one of these ? If so could you take a look at your tank for me.
I found the service manual for the series 1 which called out the tank as an Accutronics 4AB2C1A
I also found the service manual for the series II which did not call out the tank. I thought maybe the Yamaha part numbers would match but they don't.
I called our local tech today and he said he thought that the tanks would be the same but he was not 100% sure.
any of this ringing a bell for anyone

thanks,
Title: Re: Yamaha G100-115 II reverb tank
Post by: Enzo on January 26, 2017, 03:17:28 AM
You have both manuals?  great.  Forget the tank number, look at the circuit.  Do both use the same drive circuit?  If the circuits are the same, then the tanks are too.  I think both are driving low impedance loads.
Title: Re: Yamaha G100-115 II reverb tank
Post by: Scoticus on January 26, 2017, 05:10:12 PM
Enzo, Got your response this AM did not have  time to go over the schematic very well and I have to say I don't have a good grasp of how the whole schematic thing works. That said the component values were different which I expect means its a different circuit.

I got on chat with Yamaha parts department, The guy did not know what a reverb tank was although his language made me think he's an Aussie. Do they call it something else?
anyhow he said the Accutronics number is 1EB2C1A.
I was not too sure he understood so I clarified that it was a G100-115 series 2. He replied that that was correct.
Does that seem plausible?

thanks

Title: Re: Yamaha G100-115 II reverb tank
Post by: J M Fahey on January 26, 2017, 05:20:09 PM
Post-the-schematic-here  :grr :grr
Title: Re: Yamaha G100-115 II reverb tank
Post by: Scoticus on January 26, 2017, 10:56:27 PM
Here you go and thanks,
Title: Re: Yamaha G100-115 II reverb tank
Post by: phatt on January 27, 2017, 01:47:57 AM
Accutronics  1EB2C1A = 600 Ohm Drive (DC resistance ~ 60Ohms) Short tank
Accutronics  4AB2C1A = 8 Ohm drive     (DC resistance ~ 1 Ohm)  Long tank
Other than that the rest is the same but they will not be interchangeable.

One big clue here is *Obviously the tank length*,,,,, So is the Bag long or short? :tu:

Good tank Info here; https://www.amplifiedparts.com/tech-corner/spring-reverb-tanks-explained-and-compared
Phil
Title: Re: Yamaha G100-115 II reverb tank
Post by: Scoticus on January 27, 2017, 12:44:15 PM
It's a long bag, 20 inches.
Title: Re: Yamaha G100-115 II reverb tank
Post by: DrGonz78 on January 27, 2017, 02:09:42 PM
So...
G100 series 1 reverb = 4AB2C1A
G100 series 2 reverb = ??? >>> 4AB2C1A
G100 series 3 reverb = 4EB3C1B
JX30-50 type amp reverb = 1EB3C1B

As I had followed along I took time to crop all the G100 type reverb circuits to analyze them all. Also, I even started look at the Yamaha JX series amps reverb circuit too. I found a picture of the JX40 type reverb as being 1EB3C1B. At least that is the best I can make out on the picture I found online. Figured I would just post all these in one place so they are here for the looking.
Title: Re: Yamaha G100-115 II reverb tank
Post by: Scoticus on January 27, 2017, 09:01:11 PM
Awesome!
So I need to grab the 4AB2C1A.
anyone recommend a brand ?
anything to avoid?

been looking around the web and not coming up with the 4AB2C1A
is this unobtainable?
anything  else that will work?
how about the 4AB2C1B ?
Title: Re: Yamaha G100-115 II reverb tank
Post by: Enzo on January 28, 2017, 01:58:48 AM
Look up the codes for the pans.  The last chharacter is the mounting plane, and really, that is not all that critical.
Title: Re: Yamaha G100-115 II reverb tank
Post by: Scoticus on January 28, 2017, 10:40:36 AM
Right,
So, open side down but the rest will be the same.

Thanks to all you guys.
I appreciate it.
Title: Re: Yamaha G100-115 II reverb tank
Post by: Scoticus on February 06, 2017, 07:15:16 PM
OK,
So, I got my new reverb tank from MOJOTONE. 4AB2CIB, so that's correct except for the tank mounts with the cavity down rather then up.
Hooked it up and it works great. I just used regular RCA cables from a stereo.
As I said, it works but I am wondering if there is a preferred way to do this. My amp didn't come with the tank or cables so I'm wondering what is correct.
Coax cable?
I would like to have 90 degree plugs and build the cables myself or find something that fits pretty well. Any suggestions ?
thanks,
Title: Re: Yamaha G100-115 II reverb tank
Post by: Enzo on February 06, 2017, 07:45:10 PM
Write this on your wall so you can see it now and then as a reminder:

These are just guitar amps, not NASA lab equipment.  There is nothing precise about them.


It is just a reverb, like a zillion others  Plain old shielded cables are all we need.  Cheap RCA patch cords are fine.   You can probably find RCA cords that already have right angle plugs on them.  I know I used to sell them.

Just mount the pan open side down, no need to turn it into a trash bin.  I recommend you put it in a vinyl reverb pan bag.  Most places that sell pans also sell the bags.  The whole open side up or down thing is just a matter of how high the innards sit. Make sure to leave the soft grommets in the mounting holes, and NEVER screw down the pan tight.

The only real issue yet to watch for is feedback.  If you pan doesn't feedback, you have no issue.
Title: Re: Yamaha G100-115 II reverb tank
Post by: Scoticus on February 06, 2017, 08:01:34 PM
OK,
thanks Enzo, I'll remember that.
I get it, just want it to be tidy and correct.
Title: Re: Yamaha G100-115 II reverb tank
Post by: phatt on February 07, 2017, 08:02:07 AM
I read that Leo Fender used to purchase seconds for all his resistors and caps. :dbtu:
Now clowns go chasing exotic parts in the vain hope of finding the magic.  :loco

If you want a great guitar amp don't over think it. 8)
Phil.
Title: Re: Yamaha G100-115 II reverb tank
Post by: Enzo on February 07, 2017, 11:27:22 AM
I don't know that they were seconds, but they did use 20% resistors, which was the lowest grade.  Note right on many of the schematics that all readings were to be taken as +/-20%.  Cap tolerances were so poor in those days, you could almost ignore the value, or so it might seem.

Yes, when a store got in a shipment of Deluxe or whatever, one played through all of them to find the one that sounded best.  They were not remotely as uniform as they are today.

The 20% 100k plate resistor in an input stage could measure 80k to 120k and be within spec,  SO if it not hard to believe that all the accumulated parts variances added up to substabtially different sounding amps.  Even though made with the "same" parts.   Yeah, good luck chasing that sound down.
Title: Re: Yamaha G100-115 II reverb tank
Post by: J M Fahey on March 16, 2017, 10:06:25 AM
One real world example, about "fabled tone" .
One Music Electronics Forum member, John Frondelli, runs a mythical New York Service Shop, where *all*and I mean *ALL* stars, nopt only Rock but everybody else (including Disney Studios, all NY Studios, Oscar organizers .... up to and including the Navy band and CIA  :o ) send their stuff to be repaired, every month a truck stops at their door and blocks the street with stuff from, say, Megadeath or Prince or whomever is going on World Tour and wants everything checked for safety, nobody wants to rush find a Tech 8000 miles away from home.

One day he said U2 had left their truckload of equipment, and everybody asked him about a fabled Fender Princeton which allegedly had been used to record all famous band Hits.
Intrigued he checked it, since in his eyes it was "just a normal Princeton, bought at a regular store and never modded" yet it was labelled with Sharpie on a piece of paper strip: "repair but do not modify".

He checked it part by part, schematic in hand, ticking one by one what he found "normal", all he could find was that it was exactly the same as all others (at least nominally) with the single exception that a .022 coupling cap had been replaced by a .01 one.

Not a Mod, it was there from Day 1 , put straight at the Factory.

Net effect was that it cut a little Bass, so when overdriven, distortion was slightly cleaner than all others; in any case a subtle effect, not day and night.

In another Tech Forum, a member used to be a Fender VP for some time, and was asked about it, "what were they experimenting or trying to achieve and why weren´t all other Princetons built the same way, given it "worked better"

  His answer? : "don´t read too much into it, probably that day they were out of .022 caps, they *had*  to ship out some of them, and all they had on hand was .01 caps"  :o
Since apparent effect was very small and still acceptable, so be it.

This matching what Enzo said about amp to amp variations, in this case because of an actual value change, not just tolerance spread.

Clearly The Edge tried a couple Princetons at some shop and bough the one he liked most :)

Just to check the *awesome*  customer list who relie on that particular shop:
http://www.dbmproaudio.com/customers.html
Title: Re: Yamaha G100-115 II reverb tank
Post by: semjmiyta on March 24, 2017, 02:34:25 PM
Scoticus,
  I recently picked up a Yamaha G100 head awesome price and even better sound!
 I was wondering if you know or anybody on this forum would know how to go about making my own foot switches for this amp. Also have you found any literature on your amp if so where? Like an owners manual I believe mine is series 1 but I don't know for sure  how to tell.
  I was able to wire up one of my speakers from another little practice amp to tr out the head everything works I just don't have the foot switches or any info on the amp.
 Any info or help would be really appreciated.

thanks in advance
Title: Re: Yamaha G100-115 II reverb tank
Post by: J M Fahey on March 24, 2017, 06:14:32 PM
*Most*  footswitches , specially old style such as those, work by grounding the tip and sometimes the ring connector in a plug, in this case one or both "ears"  to ground.
This picture I found shows a 3.5mm "headphone"  one but principle is the same with a 6.35mm guitar one which I bet your Yamaha uses.
So get a 1/4" (6.35mm) stereo guitar plug, pull thye plastic cover, insert it in thejack you are testing and alternatively short either lug to ground with a piece of wire, and check for yourself what happens.

Then add wire as needed and a footswth at the other end, so yo again ground active lugas at will, just with your foot.

Then you mount it on a suitable, pedal type enclosure, such as the cast aluminumHammond ones or anything you can build.
Title: Re: Yamaha G100-115 II reverb tank
Post by: Alesono on January 25, 2019, 09:08:24 PM
Hello Scoticus, and you installed the 4ab2c1a reverb tank. Sound ok?.

Regards