found a chassis in my storage place :D

[norburybrook]

I am giving you a new handle Tweakburybrook

So much for "Life is to short" It's hard to stop once you start huh.

Listen to me? pot calling the kettle black!
obviously kidding around!

Tony

yep, i think I should have just left it as it was I think it's a sign of my mental state at the moment from being grounded from any physical activity due to a health issue, ironically caused by too much exercise!!! I built the amp to take my mind of things so not having the usual outlets in my life this took over and I've disappeared down the rabbit hole I've warned others of

I'm going to try keep a positive outlook on all this though and hopefully get it sorted next week and then move on.

It's also made me wonder if the ODS is actually the amp for me after all this, I started the main tweaking after plugging my 6l6 Tweedle Dee in and thinking it sounded better than the ODS in it's transition from clean to OD and I preferred the OD sound too for my own personal taste!! not something I expected but perhaps that's where I've got to after all these years

having the (limited) skills I have now means I can tweak and chase that elusive tone in my head and I know there'll be some of you guys who've already been down this road and will be smiling to yourself reading this post

someone once said : '' it's not the destination, it's the journey that matters'' perhaps they were tube amp builders/guitarists.......

onward and sideways.

M

[norburybrook]

just called in the studio on the way to a gig...

re flowed the whole OD section still nothing- all continuity tests are good.

2nd_Gen_Hybrid_w_OBLoop (1).png

I've removed the OD entrance resistors and fitted a 100k trim pot with a 220k going to a 250k drive pot.

I swapped out the 1M/180k going to the OD volume for a straight 150k going to a 250 pot.

I've left the wiring to and from the relay as before is this OK? or is there a fundamental flaw in this hence my issue?

TIA

M

[martin manning]

re flowed the whole OD section still nothing- all continuity tests are good.

:^( The answer is there somewhere... I agree it's likely loss of the signal somewhere, since DC voltages are good. Maybe some signal tracing would help locate it.

I've removed the OD entrance resistors and fitted a 100k trim pot with a 220k going to a 250k drive pot.

For the simple OD entrance I'd use a 220k from the relay (yellow lead in the right-hand layout snip above) into a 100k trimpot. 100k into 100k or 250k drive pot is typical.

I swapped out the 1M/180k going to the OD volume for a straight 150k going to a 250 pot.

That should work.

I've left the wiring to and from the relay as before is this OK? or is there a fundamental flaw in this hence my issue?

That should work fine. The signal leads from the OD common relay (yellow for OD, as mentioned above, and brown for clean) feed into the clean master and the OD entrance.

[Guy77]

It's also made me wonder if the ODS is actually the amp for me after all this, I started the main tweaking after plugging my 6l6 Tweedle Dee in and thinking it sounded better than the ODS in it's transition from clean to OD and I preferred the OD sound too for my own personal taste!! not something I expected but perhaps that's where I've got to after all these years

having the (limited) skills I have now means I can tweak and chase that elusive tone in my head and I know there'll be some of you guys who've already been down this road and will be smiling to yourself reading this post

someone once said : '' it's not the destination, it's the journey that matters'' perhaps they were tube amp builders/guitarists.......

onward and sideways.

M

I think its so true that we need to tweak our builds to find our tone. Just building the 102 or 124 or the 183 and loving it is great but I have found that I often needed to make slight changes from the standard circuit to find what I really liked. For example on my last 102 build I found that I preferred the phase inverter when the plates were set at 110k and 82k. The clean had this vintage growl that I really liked , it felt unbalanced much like a cathodyne phase inverter on your Tweedle dee would have been!



Cheers

G

[donvan]

I agree with Martin. Time for some signal tracing. As I recall you don't have a scope or signal generator but you can use your volt meter set on AC and your looper. Just feed a loop of some heavy, constant strumming into the input. Step 1: compare the output AC voltage of the preamp to the input voltage of the power amp. That will tell you if you problem is with your relays or trim pot circuitry.

[pompeiisneaks]

I agree with Martin. Time for some signal tracing. As I recall you don't have a scope or signal generator but you can use your volt meter set on AC and your looper. Just feed a loop of some heavy, constant strumming into the input. Step 1: compare the output AC voltage of the preamp to the input voltage of the power amp. That will tell you if you problem is with your relays or trim pot circuitry.

Yup exactly, or get a 1/4" to mini cable and get a phone signal gen app... sine wave in, and you're good. measure it at each gain stage for VAC and see how it grows

~Phil

[talbany]

I am giving you a new handle Tweakburybrook

So much for "Life is to short" It's hard to stop once you start huh.

Listen to me? pot calling the kettle black!
obviously kidding around!

Tony

yep, i think I should have just left it as it was I think it's a sign of my mental state at the moment from being grounded from any physical activity due to a health issue, ironically caused by too much exercise!!! I built the amp to take my mind of things so not having the usual outlets in my life this took over and I've disappeared down the rabbit hole I've warned others of

I'm going to try keep a positive outlook on all this though and hopefully get it sorted next week and then move on.

It's also made me wonder if the ODS is actually the amp for me after all this, I started the main tweaking after plugging my 6l6 Tweedle Dee in and thinking it sounded better than the ODS in it's transition from clean to OD and I preferred the OD sound too for my own personal taste!! not something I expected but perhaps that's where I've got to after all these years

having the (limited) skills I have now means I can tweak and chase that elusive tone in my head and I know there'll be some of you guys who've already been down this road and will be smiling to yourself reading this post

someone once said : '' it's not the destination, it's the journey that matters'' perhaps they were tube amp builders/guitarists.......

onward and sideways.



M

Nothing wrong with a little amp tweaking therepy I do it all the time.

Best circuit for guitar amplification IMO 5F6A Bassman/JTM 45 (Shaped the sound of Rock music)

Tony

[norburybrook]

Tony,

the second amp I ever built was a JTM45 with KT66's it would be funny if I went back to that after all these years........I've returned to the same telecaster and strat I've had for 35 years recently....it's all getting very Zen at the moment.....or I'm having my mid life crisis

it's funny that this combo was the most complex amp I've ever built and it was the first ODS type amp that worked 100% with no issues from the first power up, the perfect build and now after changing a handful of components the OD is dead and I can't work out why? well I'm sat in a hotel room somewhere so that's probably why....LOL...I fell asleep last night thinking about resistors..................no one warned me about that when I joined TAG!!!!!



M

[10thTx]

the second amp I ever built was a JTM45 with KT66's it would be funny if I went back to that after all these years

Marcus,

With your skills, ability and musical talent ……………….. you'll sound fantastic with whatever amp you are playing!

With respect, 10thtx

[norburybrook]

the second amp I ever built was a JTM45 with KT66's it would be funny if I went back to that after all these years

Marcus,

With your skills, ability and musical talent ……………….. you'll sound fantastic with whatever amp you are playing!

With respect, 10thtx

Thanks Jeff that's very kind and i appreciate the comment. As always I appreciate the help given out freely here on TAG to members new and old, couldn't have done it without you. I'm looking forward to getting back home on Monday and sorting this out....perhaps I'll re build it completely as a #183 HRM El34..........

M

[talbany]

I am giving you a new handle Tweakburybrook

So much for "Life is to short" It's hard to stop once you start huh.

Listen to me? pot calling the kettle black!
obviously kidding around!

Tony

yep, i think I should have just left it as it was I think it's a sign of my mental state at the moment from being grounded from any physical activity due to a health issue, ironically caused by too much exercise!!! I built the amp to take my mind of things so not having the usual outlets in my life this took over and I've disappeared down the rabbit hole I've warned others of

I'm going to try keep a positive outlook on all this though and hopefully get it sorted next week and then move on.

It's also made me wonder if the ODS is actually the amp for me after all this, I started the main tweaking after plugging my 6l6 Tweedle Dee in and thinking it sounded better than the ODS in it's transition from clean to OD and I preferred the OD sound too for my own personal taste!! not something I expected but perhaps that's where I've got to after all these years

having the (limited) skills I have now means I can tweak and chase that elusive tone in my head and I know there'll be some of you guys who've already been down this road and will be smiling to yourself reading this post

someone once said : '' it's not the destination, it's the journey that matters'' perhaps they were tube amp builders/guitarists.......

onward and sideways.

M

UH OOH!! Thinking of resistors is never a good sign
I know the feeling I have an amp collection most players would die for and I am never 100% satisfied.
Used to be every build I started into thinking this is going to be the one! and so far no luck. I've finally realized that's just not possible for any 1 amp to do for me.For the same reason why I like different guitars I like different amps. You have to think of them one in the same. No guitar does everything I want it to do and the more killer guitars I play the worse it gets. Same thing with amps. I think we place too high a standards on the Dumbles given all the hype surrounding them. The one thing I like about all the Dumbles is they force me to think about every note and every chord. They also sound different which forces me in different directions musically speaking. For this I like them all for one reason or another so depending on my mood or gig I have a choice now. That's how I look at it anyway.
BTW. I am thinking about a new build here not because I need another amp but I enjoy building (for now) someday I'll find another type of therapy

Tony

[stelligan]

Best circuit for guitar amplification IMO 5F6A Bassman/JTM 45 (Shaped the sound of Rock music)

Tony

Gimme one of these and an EP3 and it's all good. *Geezer alert*
No offence meant to all things Dumble here..

I also build because I enjoy the process - and troubleshooting is part of it. Just end up with a bunch of great amps piled up around me that I don't play much but, won't consider selling. Why did I sell my Tweed Bassman? Oh - tuition money, that was it..

Best of luck with the shock therapy!

[norburybrook]

Best circuit for guitar amplification IMO 5F6A Bassman/JTM 45 (Shaped the sound of Rock music)

Tony

Gimme one of these and an EP3 and it's all good. *Geezer alert*
No offence meant to all things Dumble here..

I also build because I enjoy the process - and troubleshooting is part of it. Just end up with a bunch of great amps piled up around me that I don't play much but, won't consider selling. Why did I sell my Tweed Bassman? Oh - tuition money, that was it..

Best of luck with the shock therapy!

yes, I think we're all in the same boat here

M

[norburybrook]

right then, been mulling this over while I've been away this week touring. Got home to day after a long drive and spent an hour down the studio. So, all voltages were good, all continuity was good. I started checking grounds etc and of course the OD is sent to ground when not in use so some of the grounds I was getting threw me as I'd forgotten about this . Powered up to check the connections when the relay was powered and noticed I was getting a ground after the 220k entrance resistor even when the OD was on. Bingo!! must be an under board connection there from the 2nd gen voltage divider network that was grounding the OD signal. Unsoldered that end of the resistor and flew it to a cable and all good.

so I wired in the 100k trim pot and bypassed that eyelet that was grounded. had to extend the legs and put it above the cathode caps as it was too tight to fit in. All working great now. I swapped the slope resistor from 100k to 150k like the #124 and also swapped the 4k7 NFB resistor to 3K3 as it's only a 50w rather than 100w amp and this should give the same ratio of NFB.

so it's a full on #124 low plate skyliner now as HAD intended....well almost.......100k trimmer instead of 350k. I've got it set about 25k to ground.

Decided that the board looked a mess now with all the pulling of parts and resoldering and having to fly the trim pot and some cables so in the spirit of HAD I gooped it in blue Silicone ....... LOL

I've put 6L6's in and swapped to 470R from 1.5K screen resistors. I've put is a set of russian 6n6's from an amp I built and I noticed that there's quite a difference between them, I tried a set of old short plate TAD valves and the same issue....36mA-53mA. neither are redplating and sound fine there is some slight hum though. What causes this imbalance as they were both matched sets and getting the same voltage and negative bias voltage? is it worth fitting an extra pot to balance them better?


edit: what's the relationship between the PI trim, which is set to imbalance the voltages and the bias? if I were to fit another pot do I need to change the value of both? fro example, I have say -42v going via a 10k and a 27k so 37k in total, if I split that into 2 bias pots I need double that resistance per side, yes? , can I do that with another 10k pot and 62k resistor per side, and split the 220k bias resistors?

M

[martin manning]

That is quite a large miss match, and probably the source of the hum. Try swapping the output tubes side to side and see if the idle current miss match follows the tubes or the stays with the socket. If the hot bias stays with the socket, you may be leaking HV DC somewhere.

For separate bias you can parallel another pot and tail resistor. That means drawing a bit more bias current, but it’s only a few mA. You may have to decrease the upstream resistor to get back to the same bias voltage range.

Idle power tube bias is static (zero signal) balance, and the PI trimmer is dynamic (with signal) balance.