Supro Sahara
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That may be the issue; 25W out of a pair of EL84's..CJ said:
true dat, complaint was one of the tubes putting on a light show and sounding like fried bacon,
" it has a heater voltage of 6.3V. It is capable, when used at its plate rating of 300 volts maximum, of producing 17 watts output in Class AB1 in push-pull configuration. Many guitar amplifiers routinely run EL84 tubes in excess of 400VDC, with the Traynor Guitarmate reportedly putting out 25w RMS with 2 EL84's in a push pull configuration and a B+ between 400-420VDC.
Developed by Philips in 1953 for use in the British Mullard 5-10 amplifier,[citation needed] the EL84 came to prominence when used in Watkins (and later the Vox) amplifiers preferred by many British invasion bands of the 1960s.[citation needed] When overdriven, the EL84 power tubes in these amplifiers produce a distinctive chiming, articulate, treble-heavy sound when compared to 6L6 tubes more commonly used in American amplifiers of the era such as those from Fender"
" it has a heater voltage of 6.3V. It is capable, when used at its plate rating of 300 volts maximum, of producing 17 watts output in Class AB1 in push-pull configuration. Many guitar amplifiers routinely run EL84 tubes in excess of 400VDC, with the Traynor Guitarmate reportedly putting out 25w RMS with 2 EL84's in a push pull configuration and a B+ between 400-420VDC.
Developed by Philips in 1953 for use in the British Mullard 5-10 amplifier,[citation needed] the EL84 came to prominence when used in Watkins (and later the Vox) amplifiers preferred by many British invasion bands of the 1960s.[citation needed] When overdriven, the EL84 power tubes in these amplifiers produce a distinctive chiming, articulate, treble-heavy sound when compared to 6L6 tubes more commonly used in American amplifiers of the era such as those from Fender"
phase angle at 60 Hz:
DCR:440 L: 262 H
XL @ 60 Hz: 98,721 Ohms
R/XL=440/98,721 = 0.004456978
arctan: 0.25 degrees
we have massive phase shift at the low end, (see scope shot above) but the math does not say that the DCR is the culprit,
what gives?
DCR:440 L: 262 H
XL @ 60 Hz: 98,721 Ohms
R/XL=440/98,721 = 0.004456978
arctan: 0.25 degrees
we have massive phase shift at the low end, (see scope shot above) but the math does not say that the DCR is the culprit,
what gives?
Good point Gus! I will try that next time,
here is the transformer print,
you see something different everytime you unwind a xfmr, this was no exception,
inside the can and taped to the coil was a .0047 uf cap across the primary!
don't know why, either there were some osc. issues or if it is a top secret tone tweak,
that is why the phase shift was so radical at the lower freaks,
.0047 across 262 Henries has a res point of about 147 Hz, which is about where things got shifted the most,
this coil sits on a stack of .017" non grain oriented steel and had wire that might have been made across the pond.
actual turns were 1619 T brn to red and 1577 T red to blu, so we call it 1620 ea and assume that the winder was taking certain liberties with his tolerance allowances or somebody reset his turns counter during the middle of a wind like we used to do to get back at winders who sold us some bad stuff, ;D
here is the transformer print,
you see something different everytime you unwind a xfmr, this was no exception,
inside the can and taped to the coil was a .0047 uf cap across the primary!
don't know why, either there were some osc. issues or if it is a top secret tone tweak,
that is why the phase shift was so radical at the lower freaks,
.0047 across 262 Henries has a res point of about 147 Hz, which is about where things got shifted the most,
this coil sits on a stack of .017" non grain oriented steel and had wire that might have been made across the pond.
actual turns were 1619 T brn to red and 1577 T red to blu, so we call it 1620 ea and assume that the winder was taking certain liberties with his tolerance allowances or somebody reset his turns counter during the middle of a wind like we used to do to get back at winders who sold us some bad stuff, ;D
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CJ said:
This and pic beneath is probably what local guitar amp repair guy was telling me about new gear. He feels market for well designed and built gear of this type is getting better. At least in some parts of EU, not sure about US. Hope so because we can repair or reuse less and less... Old story, i know, just reminds me of things i see too often.
How do you tell? And why? The cost saving is minimal...CJ said:
they do not make grain oriented in 26 ga, at least not over here, and you can see the grains in a grain oriented lam,
also the low perm of 5500, Grain orient is usually in the 10,000 to 20,000 range, the perm number is on the print by the core specs,
of you lace up a core with non grain Lap 1 you can get close to a 29gaM6 core laced Lap 3, which most are,
also the low perm of 5500, Grain orient is usually in the 10,000 to 20,000 range, the perm number is on the print by the core specs,
of you lace up a core with non grain Lap 1 you can get close to a 29gaM6 core laced Lap 3, which most are,
ok we have come to the conclusion that this amplifier has issues with the OPT winding topology, which resulted in tube failure. We could put a set of 84's in there and wait a year for the customer to return the amp.
Or we could fix the real problem, Why do we think the OPT is bad? they would not go to the trouble of putting that cap inside there unless there was an issue. So what do we do?
We grab a 100 EI square bobbin and wind 650 turns of #36 in four sections which sandwich three secondaries, the middle secondary being bi-filar wound like the Fisher X-100 input transformer that sound like a million bucks. So we have P-S-P-S-P-S-P instead of P-S-P,
all we have is .014" grain or sil , so now what? the inductance will go way up with the grain steel if we keep the same turns as was wound on the barn roof lams, we want the same transfer function so we match up with the speaker and cabinet, so we go from 3240 T to 2600 T and hope saturation happens when the volume knob hits 7. We will use Lap 2 like the Fisher so we don't completely freak the core out, this adds a natural air gap but keeps the inductance up compared to Lap 3.
since we are using smaller wire and less turns, we will have improved fidelity at the top end because of less stray C. This will also make the coil more stable. And we will keep the business end of the outer primary finish tucked under some copper to keep the preamp tubes from picking up too much hash. How do we do that? Reverse wind the last primary section.
How did it come out? Primary inductance is 260 Henries at 60 Hz, the original clocked in at 262 H so we good there. We have rez peaks at 45 KC and a surprise peak at 140 KC which the original transformer did not have. Next thing to do is a sound check after a bake and dip, are you with me so far?
here is the pri ind plot for the 100 EI gr or sil.
see the glitch down near 70 Hz? that is where we switch ranges on the HP 200CD, which has a very steady frequency but a not so linear voltage output, so as the knob comes back left, we get just a tad more voltage and therefore a tad more inductance. getting tired of smoothing those data points so we just leave them from now on.
Or we could fix the real problem, Why do we think the OPT is bad? they would not go to the trouble of putting that cap inside there unless there was an issue. So what do we do?
We grab a 100 EI square bobbin and wind 650 turns of #36 in four sections which sandwich three secondaries, the middle secondary being bi-filar wound like the Fisher X-100 input transformer that sound like a million bucks. So we have P-S-P-S-P-S-P instead of P-S-P,
all we have is .014" grain or sil , so now what? the inductance will go way up with the grain steel if we keep the same turns as was wound on the barn roof lams, we want the same transfer function so we match up with the speaker and cabinet, so we go from 3240 T to 2600 T and hope saturation happens when the volume knob hits 7. We will use Lap 2 like the Fisher so we don't completely freak the core out, this adds a natural air gap but keeps the inductance up compared to Lap 3.
since we are using smaller wire and less turns, we will have improved fidelity at the top end because of less stray C. This will also make the coil more stable. And we will keep the business end of the outer primary finish tucked under some copper to keep the preamp tubes from picking up too much hash. How do we do that? Reverse wind the last primary section.
How did it come out? Primary inductance is 260 Henries at 60 Hz, the original clocked in at 262 H so we good there. We have rez peaks at 45 KC and a surprise peak at 140 KC which the original transformer did not have. Next thing to do is a sound check after a bake and dip, are you with me so far?
here is the pri ind plot for the 100 EI gr or sil.
see the glitch down near 70 Hz? that is where we switch ranges on the HP 200CD, which has a very steady frequency but a not so linear voltage output, so as the knob comes back left, we get just a tad more voltage and therefore a tad more inductance. getting tired of smoothing those data points so we just leave them from now on.
Attachments
here is the Fisher coil which is actually done on a 93 EI which is just a 100 EI with a 1/16" inch shaved off the tongue,
there is one reverse wind in the primary
and two "reverse winds" in the secondary, but since they are all 1 layer, all you do is swap the start with the finish.
this print shows #34 and we used #36 so we will check for excess heat which should not be a problem,
there is one reverse wind in the primary
and two "reverse winds" in the secondary, but since they are all 1 layer, all you do is swap the start with the finish.
this print shows #34 and we used #36 so we will check for excess heat which should not be a problem,
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So it looks like someone f...ed up with the trannies, and instead of shipping them back and waiting for a (hopefully) good batch, they decided to make a run with the faulty ones. Not unheard of in manufacturing... The problem belongs to the client then.CJ said:
Some of the decisions here do not make sense; considering the high $$$, they could have used domestic suppliers, such as Hammond (after all, they chose the lowest quality).
Aaaah, greed...
