jchrisf
Well-known member
You do great work. That looks professional!
MadAsAHatter
Well-known member
I really appreciate that. I look at other's work then look look at mine and think "this shit still looks all kinds of sloppy." I guess sometimes you're your own worst critic.
griff10672
Well-known member
Looking awesome !!! Great job man !!
bennyslo
New member
Really neat and tidy. I reckon that will be some mean amp when finished
MadAsAHatter
Well-known member
Um.... I think I'm done. I've been marking off everything on the layout as I go and it looks like it's now all crossed out. I'm not ready to run through an initial startup sequence just yet though. I want to go through and quadriple check all is connected in the right place and look for any questionable solder joints. I'll take the next few days to do that and probably go through the initial startup and checks this weekend.
Oh, and I finished and mounted the badge on the headshell yesterday. I think colors matched well and it came out pretty good.
Oh, and I finished and mounted the badge on the headshell yesterday. I think colors matched well and it came out pretty good.
J
Jack Luminous
Well-known member
You could try to suck the sodler out using desoldering braid ? Nice build BTW. I only object on the piping that looks like it was done by an old english lady.
MadAsAHatter
Well-known member
I already tossed that socket. It's easier to spend $3-4 on a new one than fight trying to get solder out of a pin hole.
The piping is actually for furniture and such, but it works on amps too. It's not to everyone's taste though.
J
Jack Luminous
Well-known member
I don't like it but it's kinda funky ! Made me immediately think of my grandmother living-room curtains retainers or some such LOL
311boogieman
Well-known member
I like the piping because it is thick and because it is different.
Nice work all around my friend.
Nice work all around my friend.
MadAsAHatter
Well-known member
Well, the build is so far unsuccessful. 
I'm using Rob Robinette's start up guide. All was going well. No smoke or arcs. I was getting voltages where they should be. I did hit a minor snag where the amp squealed when first hooked to a speaker. That was just the output transformer wires being reversed (a common thing when first starting an amp). I swapped those and no more squeal. I even got as far as plugging a guitar in and getting sound. That's where the issue started.
I'm at the point of setting the bias. I plug in my bias probe to set the bias and I get no plate voltage on the power tubes. I take off the bias probe and measure the plate voltage straight from the pin and still nothing. I'm also no longer getting sound from the amp. There's still 6.3 VAC on the heaters, high voltage on the caps & whatnot, just nothing on the plates.
I've check over all the wiring again and couldn't find anything wrong there. I've read up on potential issues. Some possibilities are a bad diode or screen resistor, broken circuit in the B+, or possibly something wrong with the output transformer. I'll poke around a little more to see if I can figure something out, but I really don't have enough knowledge to troubleshoot something like this without help.
One way or another I'm going to get this thing up and running. It may just take sending it out to a pro to get it across the finish line.
I'm using Rob Robinette's start up guide. All was going well. No smoke or arcs. I was getting voltages where they should be. I did hit a minor snag where the amp squealed when first hooked to a speaker. That was just the output transformer wires being reversed (a common thing when first starting an amp). I swapped those and no more squeal. I even got as far as plugging a guitar in and getting sound. That's where the issue started.
I'm at the point of setting the bias. I plug in my bias probe to set the bias and I get no plate voltage on the power tubes. I take off the bias probe and measure the plate voltage straight from the pin and still nothing. I'm also no longer getting sound from the amp. There's still 6.3 VAC on the heaters, high voltage on the caps & whatnot, just nothing on the plates.
I've check over all the wiring again and couldn't find anything wrong there. I've read up on potential issues. Some possibilities are a bad diode or screen resistor, broken circuit in the B+, or possibly something wrong with the output transformer. I'll poke around a little more to see if I can figure something out, but I really don't have enough knowledge to troubleshoot something like this without help.
One way or another I'm going to get this thing up and running. It may just take sending it out to a pro to get it across the finish line.
jchrisf
Well-known member
Sorry for the snag.. it will be interesting for a newb like me to find out what turned out to be the issue and how you figured it out.
MadAsAHatter
Well-known member
Update:
Unfortunately I'm no closer to figuring out what's going on. I went back through the layout making sure all was wired correctly. I went through all the individuals components and they seemed fine; I didn't find any duds. Tested tubes in my tester and in another amp; no issues there. I've more than went past my limited troubleshooting and knowledge, It's time to call in a pro to take a look and find what I did wrong. Hopefully it's something simple I'm overlooking and not something major like the output transformer shitting the bed.
I need to make a quick mounting base to protect the components in shipping. After that I'll contact Rob DeAntonio (I highly trust his work) to make sure it's something he'll take in then send it over to him.
Unfortunately I'm no closer to figuring out what's going on. I went back through the layout making sure all was wired correctly. I went through all the individuals components and they seemed fine; I didn't find any duds. Tested tubes in my tester and in another amp; no issues there. I've more than went past my limited troubleshooting and knowledge, It's time to call in a pro to take a look and find what I did wrong. Hopefully it's something simple I'm overlooking and not something major like the output transformer shitting the bed.
I need to make a quick mounting base to protect the components in shipping. After that I'll contact Rob DeAntonio (I highly trust his work) to make sure it's something he'll take in then send it over to him.
jchrisf
Well-known member
That stinks.. I'm looking forward to hearing what the issue was. I'm sure it's going to be a bad part but I hope not.
H
harddriver
Well-known member
Did you have a correct bias voltage and a correct B+ without the tube installed Madasahatter?Well, the build is so far unsuccessful.
I'm using Rob Robinette's start up guide. All was going well. No smoke or arcs. I was getting voltages where they should be. I did hit a minor snag where the amp squealed when first hooked to a speaker. That was just the output transformer wires being reversed (a common thing when first starting an amp). I swapped those and no more squeal. I even got as far as plugging a guitar in and getting sound. That's where the issue started.
I'm at the point of setting the bias. I plug in my bias probe to set the bias and I get no plate voltage on the power tubes. I take off the bias probe and measure the plate voltage straight from the pin and still nothing. I'm also no longer getting sound from the amp. There's still 6.3 VAC on the heaters, high voltage on the caps & whatnot, just nothing on the plates.
I've check over all the wiring again and couldn't find anything wrong there. I've read up on potential issues. Some possibilities are a bad diode or screen resistor, broken circuit in the B+, or possibly something wrong with the output transformer. I'll poke around a little more to see if I can figure something out, but I really don't have enough knowledge to troubleshoot something like this without help.
One way or another I'm going to get this thing up and running. It may just take sending it out to a pro to get it across the finish line.
Did you do a full voltage check before installing your tubes???????????? Did you have a correct bias voltage and a correct B+ without the tubes installed? You should do that and use the voltage charts that Metroamp used to have in their step by step build instructions, they are very helpful and I always use them as a reference while I build an amp since it usually been some time between building an amp for me and it's a great refresher. I think I have the entire step by step instructions saved so PM me and I'll email them to you.
First thing to do is check where you power transformer starts feeding the board at your bias voltage circuit and your B+ before the 10K dropping resistors for the B+ circuit. If that DC voltage is not where is should be then you must recheck all your wiring on the Power transformer first and if that is all correct you need to double check all your solder joints to the power tube sockets and make sure none of them are cold joints.
Also check and make sure the polarities are correct with your diodes in your rectification circuit.
It is possible to overheat and damage the diodes in your rectification circuit if you did not use heat sinks while soldering them and induced alot of heat to them, if those are bad you will not get rectified DC for your B+. Since diodes are cheap I would removed them and install new ones using a heatsink tool on the leads that you are soldering (heat sink tool on each side of the turret of the diode you are soldering) and be quick about soldering them DO NOT put alot of heat to them. I also recommend IN4007 diodes over UF4007 diodes, they just sound better for a Marshall amp, we did multiple comparisons on Mertoamp and the UltraFast UF4007 just had this refined modern tone for some reason so you may or may not like them.
If after changing the diodes do a voltage test with all tubes removed from the amp and see what they read and see if you are getting B+ and bias voltages. If you still don't get B+ then more than likely the Power Transformer is faulty.
You can also disconnect your power transformer from the rectification circuit and double check and make sure the ACV values are within spec for that power transformer and that would also tell you if the power transformer has an issue.
Let us know how things go.
Last edited:
MadAsAHatter
Well-known member
A small update on this build. I poked around in the amp a little as I had time and still wasn't able to figure anything out. It's beyond my troubleshooting skills. So I contacted Rob DeAntonio and shipped to him over the weekend to take a look at. Hopefully he'll be able to help me get this thing over the finish line.
B
bfool
New member
Thanks for the updates - hopefully it turns out to be something easily solved! Keen to hear the details - I have ambitions to build this kit one day.
I also see that you have the Frankentone kit for your next project - I’m building that one at the moment. Check your picklist to see if you have 2*220k resistors- they accidentally used an old version for mine and I only got one. Modulus put another one in the post straight away after I told them… If they need to send you any replacement parts for the marshbar it would be a good opportunity to include that also if they used the same pick list for your frankentone.
Cheers
Dom
I also see that you have the Frankentone kit for your next project - I’m building that one at the moment. Check your picklist to see if you have 2*220k resistors- they accidentally used an old version for mine and I only got one. Modulus put another one in the post straight away after I told them… If they need to send you any replacement parts for the marshbar it would be a good opportunity to include that also if they used the same pick list for your frankentone.
Cheers
Dom
MadAsAHatter
Well-known member
I had the same thing with the picklist on the Marshbar kit. Same as yours I think they went with an older version as I was missing a couple things and had a couple left over components that weren't on the layout. It wasn't a big deal for me and no need for Modulus to ship one resistor halfway across the globe. I either already had stuff on hand or grabbed out of the Frankentone kit and will replace later on my next mouser order.
glpg80
Well-known member
Something is shorting B+ to ground and probably took out a rectifier diode in the process. That’s my assumption. Outside the obvious that the tubes are all in working order.
MadAsAHatter
Well-known member
Yeah, tubes were working fine. I tested them for shorts and put them in another amp. They worked fine.
My best educated guess is something in the power or bias circuit is out of whack. I don't have enough knowledge/experience to narrow it down beyond that. After Rob looks at it and helps me figure out what's going on I can at least add that to my knowledge base.
glpg80
Well-known member
Building them is the comparatively easy and fun part. Getting them to work is where the real fun begins. Designing something from scratch that’s never been done before is even more challenging. It takes gut to know your own limits and kudos for calling it beyond your ability so that it doesn’t ruin the fun for you in the building stage. It’s a dying art to build these and takes a lot of hours and skill. I’m excited to see what he finds and what you report back.
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