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18 Watts amp start up issues
Posted: Wed 04/14/21 12:54 pm
by davemojo
Hi All
In reality there are some issue
This is what happened so far.
Once I finished I put the limiter, the limiter was not glowing, I did it the right way but could never have strong evidence that was working or not so I am confuse.
now beside the limiter bulb light glowing or not the amp light was staying lit with power switch on and stand by switch on stand by.
No smoke no arcing and I kept it on for few mins
Switched all off and on few times no issues the light of the amp was staying on no smoke nothing suspicion but after few time on and off the fuse blown once. I could see the fuse a little black.
I replaced the fuse and today I started to test I had some alligator clips as soon as I switch the amp on this time the fuse I blown immediately, no spark no noise nothing weird, the fuse doesn't look blown like previous one so I am not even sure if the fuse has really blown. Now there is no way to put the amp on and I have no more fuse so I must get some more.
Of course when I tested the first time I never put the tubes just switch one the amp and I wanted to check today the voltage on all the tube sockets
How can I troubleshoot? It is now challenging...
Thanks
Re: 18 Watts amp start up issues
Posted: Wed 04/14/21 1:27 pm
by davemojo
What is it strange is that the limiter was built according to the instructions shown on youtube which is the same instructions and same youtube video that some of view pointed out + followed instructions on
https://robrobinette.com/ on start amp procedure
The limiter is built exactly as shown on those video and honestly you don't have to be a scientist to build that bulb limiter since is very easy.
However when I power one the amp that bulb light doesn't glow not even for a sec is off, but the current still reach the amp, and on initial test the amp was powering on and the light was on.
I could hear some very low sort of noise, very low buzzy noise but that was really low almost imperceptible. Unsure if should be there. If there was a short I would have heard some pops or maybe some smoke.
If there was a short the indicator light wouldn't have lit at all, since I had the amp on for about 5 mins last time?
Re: 18 Watts amp start up issues
Posted: Wed 04/14/21 1:36 pm
by davemojo
btw
The low noise i hear when switching on the amp, since I am sure if I replace the fuse, the amp will turn on again, is the same noise i hear on my other amp, a valve amp that I bought once years ago, is a Bluesbreaker and when on I can hear that typical low noise of a valve amp, when is on, so I believe that is normal, right?
Re: 18 Watts amp start up issues
Posted: Wed 04/14/21 2:39 pm
by Bieworm
davemojo wrote: ↑Wed 04/14/21 1:36 pm
btw
The low noise i hear when switching on the amp, since I am sure if I replace the fuse, the amp will turn on again, is the same noise i hear on my other amp, a valve amp that I bought once years ago, is a Bluesbreaker and when on I can hear that typical low noise of a valve amp, when is on, so I believe that is normal, right?
Might be your power transformer that vibrates. I always make small thin rubber washers and put them between the transformer and the chassis. It helps
Re: 18 Watts amp start up issues
Posted: Wed 04/14/21 3:23 pm
by geoff 1965
I would’nt worry about the low noise for now,you need to find out what’s blowing the fuse.can you add some close up pics of the board,tube sockets,power transformer,wiring to switches,socket etc sometimes people can spot things you might of overlooked.
Re: 18 Watts amp start up issues
Posted: Wed 04/14/21 3:28 pm
by Bieworm
You need to study your pictures thouroughly. I often see more mistakes or sloppyness on the pics I take than I see looking at the amp..
Re: 18 Watts amp start up issues
Posted: Wed 04/14/21 3:41 pm
by davemojo
geoff 1965 wrote: ↑Wed 04/14/21 3:23 pm
I would’nt worry about the low noise for now,you need to find out what’s blowing the fuse.can you add some close up pics of the board,tube sockets,power transformer,wiring to switches,socket etc sometimes people can spot things you might of overlooked.
Definitely yes I can tomorrow I will post as many picture as possible
Re: 18 Watts amp start up issues
Posted: Thu 04/15/21 2:37 am
by davemojo
Here some photos
Hope they are close enough
I ordered some slow blow fuses 1 amp getting them tomorrow.
As of today for testing only would work to temporary add a fast blow fuse 1.6 amp or would that be dangerous?
It is to just find a way to turn on the amp and troubleshoot it while is on
Re: 18 Watts amp start up issues
Posted: Thu 04/15/21 3:27 am
by davemojo
Fortunately I found some slow blow fuses they are not 1 amp but 0.8 amp for now while testing the amp should do.
Re: 18 Watts amp start up issues
Posted: Thu 04/15/21 3:30 am
by davemojo
davemojo wrote: ↑Thu 04/15/21 3:27 am
Fortunately I found some slow blow fuses they are not 1 amp but 0.8 amp for now while testing the amp should do while waiting the one with the right amperage arriving tomorrow.
Re: 18 Watts amp start up issues
Posted: Thu 04/15/21 4:11 am
by davemojo
At this point I put the 0.8 amp fuse with the amp off and stand-by switch on stand-by
As per start up procedure I turned the amp on indicator light lit up no issues all seems normal as previously mentioned and the fuse didn't blow yet. I measured the AC volts black probe ground red probe to fuse, I can read 234 Volts this is the Wall voltages. So far so good.
With the amp still on I measured the AC volts on V1 pin 9 and pin 4+5 my instructions says should read 5v to 7v the -->
https://robrobinette.com/Tube_Amp_Startup.htm says 5v so it is ok , I read instead 3.1 Volts and i checked more than once and it is is always around 3.1 volts
At this point is already 20 minutes the amp is on (switch on only) no smoke no issues definitely there is no short, (I would say so) the fact the V1 reads 3.1 volts I would say is probably OK?
Now I am going to step two powering off the amp, I will add the rectifier tube on V6 and measure DC volts (Dangerous DC Voltages) , those if I am not wrong are the one going to feed the the rectifier tube + filter cap
I'll post an update once done this will now require to switch amp on and stand-by switch on too
Side notes
The fuse didn't blow at all after exactly 28 minutes the amp was on at this point not sure why previous blown
Re: 18 Watts amp start up issues
Posted: Thu 04/15/21 4:55 am
by davemojo
Ok and now I have some more news and that explain it all
I tested now with rectifier tube on V6 the limiter is connected and I can confirm it works since there seem a short because it lighted up and stayed bright those are the exact steps
1) Rectifier tube inserted on V6
2) I put black probe to ground using an alligator clip
3) I switch the power switch on and the stand by switch on
4) I can see the rectifier tube filaments illuminating and after about 7 to 9 secs the bulb limiter light up and stays bright.
I waited to see if it would have dim out, but after 15 to 20 secs it was still bright, at this point I bet there is an issue, since it is not normal, there is a short for sure, but this is visible now when the stand by switch is turned on with the rectifier tube plugged in.
Note:
on the filter cap during the above process I can't read almost no DC voltage, I believe because is sending current to ground, correct?
What next?
I switched all off and waiting for your suggestions, I believe we need to look on the wiring on heater socket V6 I sent you pictures before. I wonder if the pink wire and gray wire are on correct V6 pin socket, when I first started I asked help here since the wire didn't match the guide but we resolved the issue and got an answer on which wires got to V6
Re: 18 Watts amp start up issues
Posted: Thu 04/15/21 5:46 am
by davemojo
Something I spot,
On previous post about the wiring I was told the following since wires color didn't match layout
"The blue & orange wires are’nt used so either cut them short and seal the ends with heatshrink or solder to an unused isolated tag.
Black is mains negative and white is mains positive “240V”
Ez81 rectifier filament are grey & pink,
The yellow and green/yellow are your centre taps for the heater filament and HT so they are soldered to ground at your star ground point."
Now the (possible issue)
The blue and orange should have been terminated, I didn't seal the ends with heatshrink but soldered them, but not to an unused tag, but to the ground used on the layout, but those tags actually were not used by anything else, it's a 3 lugs terminal strip, please check if that could cause the short, actually don't really think so since the lugs used by those two unneeded wires, aren't connected to any other ground coming from somewhere else.
Re: 18 Watts amp start up issues
Posted: Thu 04/15/21 6:32 am
by Bieworm
davemojo wrote: ↑Thu 04/15/21 5:46 am
Something I spot,
On previous post about the wiring I was told the following since wires color didn't match layout
"The blue & orange wires are’nt used so either cut them short and seal the ends with heatshrink or solder to an unused isolated tag.
Black is mains negative and white is mains positive “240V”
Ez81 rectifier filament are grey & pink,
The yellow and green/yellow are your centre taps for the heater filament and HT so they are soldered to ground at your star ground point."
Now the (possible issue)
The blue and orange should have been terminated, I didn't seal the ends with heatshrink but soldered them, but not to an unused tag, but to the ground used on the layout, but those tags actually were not used by anything else, it's a 3 lugs terminal strip, please check if that could cause the short, actually don't really think so since the lugs used by those two unneeded wires, aren't connected to any other ground coming from somewhere else.
Dave... if the blue and orange wires are additional taps for the primary voltage they should definitely NOT touch anything except isolated material or unused lugs that are not connected to anything conducting. It appears you have shorted your primary to ground
Edit: if you're using the Marshall style power trafo 18 watt from tone factory the blue wire is the 230V primary tap and the orange is the 5V secondary tap for the filament of another type of rectifier (5U4, GZ34,...)
Same deal though... you grounded your transformer on the hot wires
Re: 18 Watts amp start up issues
Posted: Thu 04/15/21 6:56 am
by davemojo
Bieworm wrote: ↑Thu 04/15/21 6:32 am
davemojo wrote: ↑Thu 04/15/21 5:46 am
Something I spot,
On previous post about the wiring I was told the following since wires color didn't match layout
"The blue & orange wires are’nt used so either cut them short and seal the ends with heatshrink or solder to an unused isolated tag.
Black is mains negative and white is mains positive “240V”
Ez81 rectifier filament are grey & pink,
The yellow and green/yellow are your centre taps for the heater filament and HT so they are soldered to ground at your star ground point."
Now the (possible issue)
The blue and orange should have been terminated, I didn't seal the ends with heatshrink but soldered them, but not to an unused tag, but to the ground used on the layout, but those tags actually were not used by anything else, it's a 3 lugs terminal strip, please check if that could cause the short, actually don't really think so since the lugs used by those two unneeded wires, aren't connected to any other ground coming from somewhere else.
Dave... if the blue and orange wires are additional taps for the primary voltage they should definitely NOT touch anything except isolated material or unused lugs that are not connected to anything conducting. It appears you have shorted your primary to ground
Edit: if you're using the Marshall style power trafo 18 watt from tone factory the blue wire is the 230V primary tap and the orange is the 5V secondary tap for the filament of another type of rectifier (5U4, GZ34,...)
Same deal though... you grounded your transformer on the hot wires
So I made a mistake there? shall I cut them off and isolate them with heatshrink instead as you mentioned once?
Re: 18 Watts amp start up issues
Posted: Thu 04/15/21 7:11 am
by JMPGuitars
davemojo wrote: ↑Thu 04/15/21 6:56 am
So I made a mistake there? shall I cut them off and isolate them with heatshrink instead as you mentioned once?
Keep it simple. Above you have a photo with the orange and blue wires connected to terminals. That's fine, as long as those terminals are not contacting anything else.
Follow your diagram:
tonefactory_18_watt_power_transformer.jpg
The green/yellow, and the yellow wires should be connected to your power amp star ground. If you're not sure what that is, read the modern ground schemes thread in my signature.
White and black wires are your mains connections.
Pink and gray are your heater connections for an EZ81 rectifier.
Green and Green are your heater wires for the rest of the tubes.
Red and Red are your high voltage AC wires going to the rectifier tube to be converted to DC voltage.
If all that is correct, then move on to the next thing and see what is shorting out that shouldn't be.
Use a highlighter to verify that you wired everything correctly, following both the schematic and layout.
Thanks,
Josh
Re: 18 Watts amp start up issues
Posted: Thu 04/15/21 7:16 am
by davemojo
Yes thanks just for the sake of being 100% sure I cut the blue and orange from the terminal and isolated them with heatshrink the short remain. Now I am following Josh steps and thanks Bieworm too
for his reply
Re: 18 Watts amp start up issues
Posted: Thu 04/15/21 7:39 am
by davemojo
Here the checks Josh
1) The green/yellow, and the yellow wires should be connected to your power amp star ground.
This is done correctly I checked, the terminal strip is a 3 lugs one with a jumper connecting together all 3 lugs as per kit instructions
2) White and Black seems correct black goes to main switch and White goes to fuse box.
3) Pink and gray both goes to V6 EZ81 Socket pin 4 pink and pin 5 gray so seems correct too
4) Red and Red are going to rectifier V6 EZ81 pin 1 and pin 7 seems correct too
I attached 2 photos one closely shows the 2 green going to V5 4 and 5
At this point from there there is the daisy chain that I made with black and white wire that connect all the other sockets so the short could be somewhere from this point ahead the white leaves the pin 4 twisted with the black that leaves pin 5 of that V5 socket and they respectively reach the same on V4 pin 4 (white) and pin 5 (black) this is the same down to all the other remaining socket but need to double check if there is solder touching the closets pin
Re: 18 Watts amp start up issues
Posted: Thu 04/15/21 8:10 am
by Bieworm
Yes
Re: 18 Watts amp start up issues
Posted: Thu 04/15/21 8:13 am
by davemojo
Ok and now how to proceed? I am rechecking but is getting not so easy but I must get, somehow, to the bottom of this