- The 10M45 looks like it was installed OK.
- Did you line up the tube sockets such that the notch in the hole aligns with the notch on the silkscreen? Geoerge has a picture of this here:
Put your meter in the ohms setting. Touch the leads together and it should read very close to 0 ohms.
Now, measure between T1-RED-YEL and the side of R4 closest to the edge of the board? What is the resistance in ohms?
Also, what is the rating of the fuse? How many amps, fast or slow blow?
- Did you line up the tube sockets such that the notch in the hole aligns with the notch on the silkscreen? Geoerge has a picture of this here:
nikolas812 said:
Put your meter in the ohms setting. Touch the leads together and it should read very close to 0 ohms.
Now, measure between T1-RED-YEL and the side of R4 closest to the edge of the board? What is the resistance in ohms?
Also, what is the rating of the fuse? How many amps, fast or slow blow?
korneluk said:- The 10M45 looks like it was installed OK.
- Did you line up the tube sockets such that the notch in the hole aligns with the notch on the silkscreen? Geoerge has a picture of this here:
Put your meter in the ohms setting. Touch the leads together and it should read very close to 0 ohms.
Now, measure between T1-RED-YEL and the side of R4 closest to the edge of the board? What is the resistance in ohms?
Also, what is the rating of the fuse? How many amps, fast or slow blow?
Yes the tube sockets were lined up correctly
Where do you put the red probe and the black probe? Does it matter. I get different reading each way. Neither stay the same. They change the longer I hold the probes on..
With the red probe touching T1- red yellow and the black the probe touching R4 closest to the edge it reads. Well. SOmething different every time. The last time read 2.512m some times it read 1.9 sometimes it reads 39.2 and it changes the longer you hold them on there..
I also have fast blo fuses. 1.6a and 2.5a
I have only used the 1.6a so far...
Nick
nikolas812 said:
Ooops! The KT-88 tubes you're using consume 1.6A each on the heaters alone, plus 2A for the 5AR4 rectifier heaters, plus .3A for the 12AT7, plus the B+ current draw.
You better get some 5A slow blow fuses and try again...
Blew it.
the 12at and 5ar4 started to light up then 5ar4 start flickering with blue and the fuse blew...
Nick
the 12at and 5ar4 started to light up then 5ar4 start flickering with blue and the fuse blew...
Nick
nikolas812 said:
Blue flickering means arcing due to excessive current draw.
Can you please check that capacitors C1 and C2 are installed with the right polarity - i.e. the (-) negative side to ground?
korneluk said:
THIS IS NOT GOOD ADVICE!!!!!
In a transformer, incoming power is equal to outgoing power (in an ideal transformer).
Power = Volts x Amps
Therefore Volts x Amps in = Volts x Amps out.
Your transformer is rated for something like 120 volts in, 750 volts out at 200mA, 6.3 volts out at 6A and 5.0 volts out at 3A.
750 volts at .2A = 1.25 Amps at the input
6.3 volts at 6A = 0.315 Amps at the input
5.0 volts at 3A = 0.125 Amps at the input
TOTAL = 1.69 Amps.
You should use a 2 or 2.5 Amp SLOW BLOW fuse.
Chris
nikolas812 said:
As mentioned before, if you have a 5A fuse (BAD!!!!!) and blue arcing in the rectifier, you have a short.
I see you don't have the FREDs installed. That is good. You have a whole bunch of wires on that work bench. Plenty of opportunity for errors there. Check everything on and off the board. Make sure you have no shorting unused wires from the power transformer.
When you have done this, take a systematic approach. As there appears to be a high current draw downline of the rectifier, I would first remove the rectifier and make sure that all of the heaters are working on the power valves and input valve. They should be OK. Then start looking for shorts, damaged components and mis installed components...
korneluk said:
I suppose I could write it a different way, using Volt Amps
750volts .2A = 150 VA (Volt Amps)
6.3volts 6A = 37.8 VA
5volts 3A = 15VA
Total 202.8 VA
Input voltage 120 volts therefore 202.8 / 120 = 1.69 Amps drawn. 2.5 Slow Blow fuse required
chrish said:
Chrish,
My bad, I should have been more explicit why I made the recommendation I did.
The 6K7VG is rated for 117V
750V 150mA
6.3V 5A
5V 3A
for a combined total of 159VA.
At 159VA/117 = 1.36A.
Now, using the rule of thumb I learned from old HAM radio guys for troubleshooting equipment, take 3x the primary current or the total heater current draw (whichever is greater) to calculate the fuse rating.
If this is exceeded and the fuse blows, then there is a major fault. This is just a troubleshooting back of the envelope calculation, that is why I recommended a 5A fuse.
Again, my bad for not giving more details.
I've checked and re checked the power transformer wiring.
Everything seemd correct.
Except... The green and yellow wire. Its not hooked to anything.
On top of the transformer it says.. Sec2 6.3VCT, 5a Grn-Grn/yel-grn
Should the yellow green be hooked up to the two green wires somehow?
Nick
Everything seemd correct.
Except... The green and yellow wire. Its not hooked to anything.
On top of the transformer it says.. Sec2 6.3VCT, 5a Grn-Grn/yel-grn
Should the yellow green be hooked up to the two green wires somehow?
Nick
No, the center tap of the filament winding is not connected to anything.
An externally hosted image should be here but it was not working when we last tested it.
I've checked and re checked the power transformer wiring.
It looks good to me.
went over evey solder joint on the board and they look good.
What didn't look good I cleaned and made look good.
Also all I have is fast blo fuses and I am quickly running out..
A slow blo wouldn't be problem would it??? I wouldn't think so but I don't know much about it.
Could I have a bad rectifier tube?
also. everythin is grounded. I mean everything. The rcas the binding posts each transformer choke and cap are all grounded to the IEC ground. Could I have them grounded wrong somehow?
I just don't know what esle to look for.
Should I put the freds in and try and run it without the recitfier?
Nick
It looks good to me.
went over evey solder joint on the board and they look good.
What didn't look good I cleaned and made look good.
Also all I have is fast blo fuses and I am quickly running out..
A slow blo wouldn't be problem would it??? I wouldn't think so but I don't know much about it.
Could I have a bad rectifier tube?
also. everythin is grounded. I mean everything. The rcas the binding posts each transformer choke and cap are all grounded to the IEC ground. Could I have them grounded wrong somehow?
I just don't know what esle to look for.
Should I put the freds in and try and run it without the recitfier?
Nick
korneluk said:
No problem, just want to make sure we are all on the same page. You had me scratching my head making sure I was not giving incorrect information
🙂
As for the unused power transformer leads. Make sure that the ends of the wires are insulated (I use a little heat shrink here) and then use a cable tie to neatly hold them out of the way.
The motor run cap is not polarised, so connection should not matter as long as it is wired correctly. It looks like all of you electrolytics are installed with correct polarity...
It is a waste (of fuses and other parts) to just replace items without finding the problem. Re-check for any shorts across traces on the board. Check all installed components are correct value and no burnt out resistors etc. Re-check all off board wires. There are quite a lot here, plenty of scope for error. Any reason they are not screwed in to the terminals rather than soldered to the board?
Also, a previous short may have blown the rectifier. I have had this happen, but don't just replace without exhausting other fault-finding as you may just end up blowing another fuse and rectifier...
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