Gibson GA-16T/18T done

[Blooze]

Finally. Thanks to everyone who’s helped me with my first guitar amp.

[Blooze]

Innards:

[Lectroid]

Blooze, can I ask where you bought your chassis?  Was it pre-drilled?

[Blooze]

Blooze, can I ask where you bought your chassis?  Was it pre-drilled?

ZH Music Parts on ebay.  It was predrilled on the top. The face/rear were blank. The power transformer hole was for the typical laydown type, so I had them send a small plate to cover it so I could mount the upright transformer.

https://www.ebay.com/str/zhmusicparts

[Lectroid]

Thanks.  Those are good.  I've used his chassis' before.

[kagliostro]

Nice

I like the idea of the round holes on the cab 

Franco


p.s.: Do you have a Layout that you can share ?

[punkykatt]

Very nice! I would love to hear some sound samples.

[72Blazer]

Ditto on the sound.  Very nice craftsmanship throughout.  Definitely one of a kind.

Vr
J

[Blooze]

Very nice! I would love to hear some sound samples.

No you wouldn’t, lol. I can make some power chords and a little more, but that’s about it. I enjoy the building of pedals and stuff and seeing how they sound more than learning how to play. For instance, I’ll breadboard a pedal design, build it up, play with it a few times and up on the shelf it goes. I’ll see if I can work something up though that doesn’t sound pathetic. Right now I  need to make a speaker cab for it as all I have is a 2x12 jet city. I have a couple 10” ragin Cajuns a friend gave me years ago I should use.

[Blooze]

Nice

I like the idea of the round holes on the cab 

Franco


p.s.: Do you have a Layout that you can share ?

I need to update a rough DIYLC (or was it in Inkscape ??) I could post that possibly later this week.

[kagliostro]

Many Thanks

Franco

[bmccowan]

Well done Blooze! Very tidy work throughout.

No you wouldn’t, lol.

I can relate to that.
As you know I built one at about the same time - I have an old Gibson cab that it'll go into when I get around to it. But I've been playing it plugged into an ext cab. It's a great sounding circuit. I have a brownface Princeton and I like the Gibson better. Its not as loud - lower B+ voltage and cathode bias - but the tone is sweeter. Highly recommended for folks wanting to build a simple PP with trem.

[Blooze]

Well done Blooze! Very tidy work throughout.

No you wouldn’t, lol.

I can relate to that.
As you know I built one at about the same time - I have an old Gibson cab that it'll go into when I get around to it. But I've been playing it plugged into an ext cab. It's a great sounding circuit. I have a brownface Princeton and I like the Gibson better. Its not as loud - lower B+ voltage and cathode bias - but the tone is sweeter. Highly recommended for folks wanting to build a simple PP with trem.

Thanks!  I'm still not satisfied with the trem, but to be honest was tired of messing with it and I can put a pedal in front if I really want reliable, consistent tremolo. Even with the LED substitution the depth control is very limited (between 10-1 o'clock). I thought it was working well last time I tried it before mounting in the cab, but evidently not, as when I get it to kick on both controls appear to only work in about 1/3 of their range.  I'll try playing it again this weekend though.

[Blooze]

Many Thanks

Franco

Here's the layout I have.  It was done in Inkscape. I'm down to my work laptop most of the time and I can't install Java to run DIYLC due to restrictions. I wish that program was in something besides Java. If you need a DIYLC file I may be able to get one this weekend.

[bmccowan]

Thanks!  I'm still not satisfied with the trem, but to be honest was tired of messing with it and I can put a pedal in front if I really want reliable, consistent tremolo. Even with the LED substitution the depth control is very limited (between 10-1 o'clock). I thought it was working well last time I tried it before mounting in the cab, but evidently not, as when I get it to kick on both controls appear to only work in about 1/3 of their range.  I'll try playing it again this weekend though.

Hmm - When I get home I will try mine. I do not use trem very often and when I do it is slow and mild

[Platefire]

I like the hole patterns in the front and back plates of cab. Something a little bit different butserves a very good purpose. It made me recall the old houses of the 1800's way before air conditioning was ever thought about, many houses had a hallway right down the centerof the house with the rooms on either side. This was called a breezeway to get a little aircirculation to the rest of the house. So you have a very artful Breezeway for the tubes. Great job!

[kagliostro]

Many Thanks for sharing the Layout

about the tremolo consider to give a try to the Sluckey's Tremonator

Franco

[Blooze]

Many Thanks for sharing the Layout

about the tremolo consider to give a try to the Sluckey's Tremonator

Franci

Maybe on the next one. I’m not one to mod a lot once I have something pretty much done.

[kagliostro]

Yes, I can understand

http://sluckeyamps.com/trem/trem.htm

Franco

[bmccowan]

Thanks!  I'm still not satisfied with the trem, but to be honest was tired of messing with it and I can put a pedal in front if I really want reliable, consistent tremolo. Even with the LED substitution the depth control is very limited (between 10-1 o'clock). I thought it was working well last time I tried it before mounting in the cab, but evidently not, as when I get it to kick on both controls appear to only work in about 1/3 of their range.  I'll try playing it again this weekend though.

Hmm - When I get home I will try mine. I do not use trem very often and when I do it is slow and mild

I made it home and fired mine up. Both trem controls have an effect over their full range. The depth is just about nil on 1, but that is how it should be IMO. It gets into a quite noticeable range around 3 (3 of 12 - I have 1-12 range on my pots which might be 2 better than what you have  ) and clearly gets deeper up to about 10. 10-12 not much noticeable change - no surprise. Speed also has full range - but subtle at the extremes. So I think something is amiss with yours. I looked at your schematic to see if I could spot any differences. The MV is all I see. If you dime the MV to take it out of the circuit - does that change the trem response. I Don't know why it would. I imagine you tried swapping the tube? LED? and checked that you did not misread a resistor? Since you are tired of messing with it, you likely did all that.
Playing it today reminded me how nice the trem is on this amp. Kagliostro mentioned the Sluckey Tremonator circuit. I have done that in two Fenders that used roaches. Its a great mod for those circuits. But no need for that with the 18T - the trem is smooth and lush. If you take a break and then go back to it - you will likely find the issue.

[Blooze]

Thanks!  I'm still not satisfied with the trem, but to be honest was tired of messing with it and I can put a pedal in front if I really want reliable, consistent tremolo. Even with the LED substitution the depth control is very limited (between 10-1 o'clock). I thought it was working well last time I tried it before mounting in the cab, but evidently not, as when I get it to kick on both controls appear to only work in about 1/3 of their range.  I'll try playing it again this weekend though.

Hmm - When I get home I will try mine. I do not use trem very often and when I do it is slow and mild

I made it home and fired mine up. Both trem controls have an effect over their full range. The depth is just about nil on 1, but that is how it should be IMO. It gets into a quite noticeable range around 3 (3 of 12 - I have 1-12 range on my pots which might be 2 better than what you have  ) and clearly gets deeper up to about 10. 10-12 not much noticeable change - no surprise. Speed also has full range - but subtle at the extremes. So I think something is amiss with yours. I looked at your schematic to see if I could spot any differences. The MV is all I see. If you dime the MV to take it out of the circuit - does that change the trem response. I Don't know why it would. I imagine you tried swapping the tube? LED? and checked that you did not misread a resistor? Since you are tired of messing with it, you likely did all that.
Playing it today reminded me how nice the trem is on this amp. Kagliostro mentioned the Sluckey Tremonator circuit. I have done that in two Fenders that used roaches. Its a great mod for those circuits. But no need for that with the 18T - the trem is smooth and lush. If you take a break and then go back to it - you will likely find the issue.

I’ve just pulled the amp. Check the parts values from the 270K onward and all are what are on my schematic (270k,510k, 2.2M, 68k, .33u, .033u, .022u, .022u).

What values did you use and what voltages did you have?  I can see the LED blink rate go faster but once I hit about 6 on the rate it maxes out and then I have to turn the depth and rate to zero to get it to start again. Depth doesn’t do much at all. Basically it only works in one little short range with both adjustments between 3-5.

[bmccowan]

Those same values, as I wanted slower trem than stock. I will check voltages, but I just had a bourbon and I never touch live amps if I've had either liquid or dry refreshments.
It seems like;

I can see the LED blink rate go faster but once I hit about 6 on the rate it maxes out and then I have to turn the depth and rate to zero to get it to start again. Depth doesn’t do much at all.

will be good clues for some of the more expert folks here.
When I first tried the LED trick I used an LED with a pre-assembled current limiting resistor. Sluckey pointed out my mistake and once corrected, it worked fine. He and others here can likely help you better than I can, but I can continue to give you info from my build.

[bmccowan]

Voltage chart from mine:
Note that I used the first half of V2 for the trem circuit, so the voltages are different
And I notice that my amp is starting with a higher B+, but your V2 plate voltage in the trem circuit is higher?? I'm not sure why and I'm not sure if it is significant.

[sluckey]

When your tremolo stops is the LED still flashing? The depth control should not affect the LED flashing.

And I notice that my amp is starting with a higher B+, but your V2 plate voltage in the trem circuit is higher?? I'm not sure why and I'm not sure if it is significant.

His plate voltage is higher because his tube is not conducting as much as your tube. Maybe a weak tube, plate resistor, grid resistor. Check'em all.

[Blooze]

Ok. I checked all resistors and they are correct. I swapped V1 and V2. Virtually same voltages except at V1 plates which is 5V higher and V2A plate is 5V lower while V2B pin 6 which is now 181V instead of 191V. My AC mains voltage is 2V less than the one when I measured for the schematic I attached though.  Trem works much better. These are both new JJ ECC83S’s from Eurotubes.

Edit: swapped in one of two old 12AX7’s I have on hand. V2B plate went to 166V and V2A plate to 190V. Trem seems a little deeper for lack of a better description. Speed works turned clear down very well and gets beyond my ability to notice it a little past 1/2 way. The tube is a Sylvania 12AX7 (ECC83, 7025).

[Blooze]

When your tremolo stops is the LED still flashing? The depth control should not affect the LED flashing.

And I notice that my amp is starting with a higher B+, but your V2 plate voltage in the trem circuit is higher?? I'm not sure why and I'm not sure if it is significant.

His plate voltage is higher because his tube is not conducting as much as your tube. Maybe a weak tube, plate resistor, grid resistor. Check'em all.

The depth control doesn't affect the LED flash rate. If you read the previous post I swapped in an old Sylvania 12AX7 I had and that seemed to make the trem stronger (more noticeable). I seem to have full depth range when the trem is working and I've squeezed a little more trem out on the upper end before it quits and the lowest rate setting.  Curious what your thoughts would be to maximize this any more?  Or is it a matter of getting the "right" tube in the V2 slot?

Thanks for everyone's help.

[bmccowan]

I was hanging back to see if Sluckey had any ideas, as he has knowledge far beyond mine. But I think as long as you have a strong 12AX7 in there, I think you are ok with the tube. I know you said that you checked that the right resistors were in place, but did you also check them with a meter for actual resistance? Faulty pot maybe? 

[Blooze]

I was hanging back to see if Sluckey had any ideas, as he has knowledge far beyond mine. But I think as long as you have a strong 12AX7 in there, I think you are ok with the tube. I know you said that you checked that the right resistors were in place, but did you also check them with a meter for actual resistance? Faulty pot maybe?

I did check everything with a meter as well. I think it may be a matter of the tube.  I've done a little digging and see several references to a trem not working correctly because the tube is weak. These are brand new tubes, but that doesn't really mean much. The plate voltage sure dropped when I put the vintage tube in though. It's miles better than what it was.

[bmccowan]

I agree that you need a strong tube for trem to work right - if its miles better maybe you are ok. But if it is still cutting out on you something is not right. But sometimes we just need to take a break from chasing the rabbits, eh?

[Blooze]

Definitely tube dependent. I swapped the new JJ’s. One works decent with plate voltage close to 190 like the other one (which barely works). Probably the order I had them in when testing. I tried another old TungSol I had with a plate voltage of 182 or so which worked better yet. None of them work as good as the Sylvania with the lower plate voltage at 165. That’s all the AX7’s I have left on hand.