Dr.Z For All

Tube or solid-state, this section goes to eleven!

Re: Dr.Z For All

Postby jaxx » 06 Jan 2010, 13:56

hi Dan,


mazerati gt have a 10W 50ohm resistor only. it is the el84's cothode resistor in parellel a 250uf sp.atom.

see the picture.
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Re: Dr.Z For All

Postby bkeck » 04 Jul 2010, 17:29

i finally worked on building the stangray. Unfortunately, i am getting very little voltage pin 8 of the GZ34. I have tried 2 GZ34's (a new one and one i know works). I have double checked all wiring per the layout. The transformers are new. Any ideas out there, please? I'm stuck.
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Re: Dr.Z For All

Postby macm75 » 04 Jul 2010, 17:59

I assume you mean DC. Do you have 5VAC on the heaters (2,8)? Do you have the appropriate AC (PT secondary) across the plates (4,6)?
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Re: Dr.Z For All

Postby bkeck » 05 Jul 2010, 08:17

Thanks for responding.
Yes, 5.25vac across 2 & 8 and 570vac across 4 & 6.
DC from 8 is less than 5v
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Re: Dr.Z For All

Postby jbrew73 » 12 Jul 2010, 03:24

did you ground the 5v center tap? it should not be grounded, just leave it floating.
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Re: Dr.Z For All

Postby SirElwood » 12 Jul 2010, 08:38

jbrew73 wrote:did you ground the 5v center tap? it should not be grounded, just leave it floating.


No no no! Do not leave it floating. If you have a 5V center tap, you should take your DC from there!
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Re: Dr.Z For All

Postby bkeck » 13 Jul 2010, 01:42

the PT does not have a CT on the 5v winding. I found the issue (disassembled and started from scratch) it was a poor ground on high voltage winding... the CT was not crimpped hard enough to the star ground ring lug.

that issue taken care of, i got it to work. It sounds pretty good, but if i turn it above '3', the bottom end gets a very loud ugly distortion. i will be looking at the coupling caps or even try a different Ef86... any other ideas...or possible variations from the layout on found in this thread?

PS. if anyone is looking for the transformer set, i got mine from transformerdesignandsupply.com.... very helpful and kind people.
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Re: Dr.Z For All

Postby macm75 » 13 Jul 2010, 02:41

You learned a lesson - don't crimp, always solder :-)
I built the Z28 a couple months ago and I see the driver circuit is close. FWIW, my B+ for the EF86 is 285V, anode voltage is 75V, cathode voltage is 1.75V. B+ for the 12AX7 is 290V, anode voltages are 235/230V, cathode voltage common to the triode pair is 59V.
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Re: Dr.Z For All

Postby bkeck » 13 Jul 2010, 05:06

macm75 wrote:You learned a lesson - don't crimp, always solder :-)
I built the Z28 a couple months ago and I see the driver circuit is close. FWIW, my B+ for the EF86 is 285V, anode voltage is 75V, cathode voltage is 1.75V. B+ for the 12AX7 is 290V, anode voltages are 235/230V, cathode voltage common to the triode pair is 59V.


LOL! yep now i crimp and then solder leads to the starground. i'll check my voltages. Thanks again!
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Re: Dr.Z For All

Postby darkbluemurder » 20 Jul 2010, 13:33

bkeck wrote: It sounds pretty good, but if i turn it above '3', the bottom end gets a very loud ugly distortion. i will be looking at the coupling caps or even try a different Ef86... any other ideas...or possible variations from the layout on found in this thread?


I built a Stang Vee, i.e. a Stang Ray with 2 6V6s. It is the best clean amp I have - think Brad Paisley - but not very loud. I found that it is important to use no larger than 0.01uf for the input and output coupling caps on the PI. Otherwise the tone will become too bassy, especially at some settings of the tone control. While I don't have the ugly distortion problem the amp seems a bit low in gain and output, even though it matches the sound samples published on YouTube quite well. I strongly consider to change the output transformer and upgrade to 5881 or 6L6 to get some more oomph.

Cheers Stephan
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Re: Dr.Z For All

Postby bkeck » 26 Jul 2010, 03:05

Found the problem. i didn't have the bottom of the chasis on tight enough (yet one more ground issue, man i hate those).

I checked the voltages against the layout and found that i was a little high but i was testing it with out a load. i have since played out with it at four shows (using my Fender Custom Vibrolux as a 2x10" cab) and it sounds absolutely awsome!!! I'm so pleased with it that i will be using it this coming weekend to open for Rodney Atkins.

Thanks for the responses and suggestions. you kept me from giving up on a great project!!!
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Re: Dr.Z For All

Postby ukbrightonbloke » 15 Sep 2010, 11:00

Hi all

I have built a couple of Torres amps and experimented and thought I woul have a go at a hybrid based on the route66 adding a maz channel, maybe a maz66??

Anyway, have been doing the layout for this based on best practice , valve distances etc all fitting into a JTM 45 type chassis. I will post all the suppliers I have found on here from the research I have done. I am based in UK.

I have decided on the Hammond 1650HA OT (the winding for screen is 41% in this OT whereas I believe the route66 OT is 43%) the transformer will probably saturate sooner but I dont mind that! My sticking point is the PT, I keep looking at spec sheets for KT66 used in this config and need some advice/guidance as I cant seem to get a definitive anode(plate) current figure for the kt66. The Hammond 374BX has all the windings , a little hot (i beleive its a 373-0-373 in the rt66 but this is a 375-0-375, good enough for rock n roll!) but the current at 175ma seems too low for fthe draw of the output tubes in this config biased at 36ma? the only other transformer I can find that would do the job is a custom wound from Sowter which is over £100 more.

Any thoughts would be great.

Will share any info i find during build of this project.

Thanks in advance
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Re: Dr.Z For All

Postby darkbluemurder » 21 Sep 2010, 14:17

Hi,

a 375-0-375 power transformer would give you about 480-490V with a GZ34/5AR4 rectifier. This is close enough to what I remember having read about the plate voltage in a RT66 - 470V. But the current of 175ma seems a bit low indeed - I would look for something in the 250ma region.

Cheers Stephan
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Re: Dr.Z For All

Postby ukbrightonbloke » 15 Mar 2011, 09:26

Thanks for info about PT.

Thanks to all that post on here especially photos etc.

Does anyone have the B+ voltages for the Maz nr? I am looking to build a hybrid so need to design a power supply but would like to know the voltages required. I did try math and duncans psu designer based on values in drawn schematics but they dont tally.

Heres some resources for uk builders:

http://www.ampmaker.com/home-1-0.html
http://www.bluebellaudio.com/
http://www.torresamps.com/
http://modulusamplification.com/
http://www.hotroxuk.com/ (great valve selection)
http://www.valvepower.co.uk/

Hope this helps some uk. European builders

Thanks in advance.
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Re: Dr.Z For All

Postby DrNomis » 15 Mar 2011, 18:13

shicky wrote:Hi, I am trying to build mini z for my first tube amp project.
I have a few questions.

1. It was impossible for me to get 40uF 450V and 20uF 450V capacitors used in Rectifier (Bridge?) section.
I was able to get 47uF 450V and 22uF 450V.
Values didn't really make a huge difference in PSU Designer graph but I would like to make sure if I can use those.

2. What should I use for Rectifier Diodes, 1N4001?

3. What would be the fuse size? is 1A sufficient?

I would really appreciate your help.

- shicky -




You shouldn't have any problems using those value capacitors, capacitors usually have a tolerance of anywhere between +- 20% of the marked value, just make sure the voltage rating is equal to, or greater than the supply, in this case 450V DC should be fine.... :)
Genius is not all about 99% perspiration, and 1% inspiration - sometimes the solution is staring you right in the face.-Frequencycentral.
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Re: Dr.Z For All

Postby G5120fx » 28 Oct 2011, 17:21

Is a Turret layout for the Mini Z out there?
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Re: Dr.Z For All

Postby macm75 » 28 Oct 2011, 21:31

G5120fx wrote:Is a Turret layout for the Mini Z out there?

I've not seen one. All that I have seen are pictures of the layout and "Mini-MeeZ" schematic. Easy to figure it out.
And who needs the layout anyway - lay it out yourself.
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Re: Dr.Z For All

Postby ukbrightonbloke » 10 Aug 2012, 20:40

Thought I would share my build.

Used Hammonds for the PT & OT, Circuit is based on Route 66 with MAZ Jnr channel added with switching. Waiting set of tubes to complete.

Hope you like

Awaiting tubes

P8080014.JPG


Scratched the back paint :(

P8080015.JPG


Inside

P8090023.JPG


Will tweak some values once fired up with proper cab and tubes

CM
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Re: Dr.Z For All

Postby Greenmachine » 11 Aug 2012, 00:54

Very nice build.
"[Y]ou want sketchy, dude? I breadboard on a door." -- RnFR, 2011
"This amp is freakin loud, like crazy, I'm going to kill pets loud." -- mich, 2011
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Re: Dr.Z For All

Postby macm75 » 11 Aug 2012, 04:42

ukbrightonbloke wrote:Hope you like


How can one not? Beautiful/professional work.
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