Driver to drive?

boB <boB@k7iq.com> wrote:
On Thu, 7 Nov 2019 19:40:03 -0800 (PST), Phil Allison
pallison49@gmail.com> wrote:

bitrex wrote:

-------------


** Very devious thinking there.

The actual scenario is quite simple and what many musos do all the time.

Guitarists that is ...


..... Phil



Related to some kind of distortion or effect box before the input, like
maybe one of those tube compressor/limiters that have a transformer
coupled output and put out a hot signal. Or running the guitar into a
mic preamp first and using similar output stage.



** Normal use, no unusual devices and something he had done many times.



..... Phil



Smashed his guitar on the amp on stage of course trying to be Jimi
Hendrix
Click to expand...

The guitarist follows this ritual first, before the smashup:

1. power on the amp
2. turn the amp gain all the way up
3. turn the guitar gain all the way up
4. stand in front of the speaker and face it
5. plug the guitar into the live amp
6. turn the gain down a smidge to stop the shrieking feedback
7. if U1's still alive tune the guitar otherwise exit the ritual
8. strum the A chord
9. strum the D chord
10. strum the E chord
11. play an ascending arpeggio
12. play a descending arpeggio
13. pick through the first few bars of "Stairway to Heaven" a few times
14. Go back to standing in front of the amp and face it to create the
shrieking feedback necessary for a Hendrix state of mind.
15. play a rough rendition of the "Star Spangled Banner" once

Thank you, 73,

--
Don Kuenz KB7RPU
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.
 
On Friday, 8 November 2019 12:52:33 UTC, Phil Allison wrote:

The output transformer appears to be shorted when neither of
the speaker outputs are connected.

John
 
I'm going to guess the muso would first plug his cable into the amp and THEN plug it into the guitar.

The tip of the phone plug would touch the guitar first and couple whatever static charge on him directly into the input of the op amp.

Mark
 
On Friday, November 8, 2019 at 9:25:10 AM UTC-8, Alex Borroughs wrote:
> I've been looking for a cheap, possibly DIY solder smoke solution.

The HEPA filter scheme is intended to trap solid particles, like pollen; fumes from soldering
are typically resin (RMA flux) or organic vapors (from a variety of alcohol-soluble
and water-soluble fluxes). A LOT of soldering is required to emit as much as
a gram of material from these sources.

For solder smoke, anything that is a solvent for those materials, should absorb efficiently,
it doesn't have to be a HEPA filter (because it can adhere-to/dissolve/trap the
chemical substances of interest, not just particles in a size range).

Get a little glycerine and spray it onto any suitable air filter medium, it'll
work on light-alcohol-soluble resin flux, and is mildly hygroscopic so will
also stick to any water-soluble droplets. Once a year, replace the dirty
filter. Or, maybe just use a mesh that can be run through the dishwasher?

<https://www.mcmaster.com/reusable-air-filters>
 
On 11/7/19 8:34 PM, Phil Allison wrote:

--------------------

Question 2:

The same amp has a shameful design problem with the output stage.

Wilful stupidity.

Bet nobody gets it.



.... Phil
Click to expand...

The feedback around the output transformer back to IC4 is DC coupled,
the line out jack is DC coupled too, and if the line out jack is
connected and there's a DC offset/ground potential difference on
whatever you plug it into you get a big DC offset at the output of both
the IC-4 drivers
 
fredag den 8. november 2019 kl. 16.49.21 UTC+1 skrev jrwal...@gmail.com:
On Friday, 8 November 2019 12:52:33 UTC, Phil Allison wrote:

The output transformer appears to be shorted when neither of
the speaker outputs are connected.
Click to expand...

for a tube amp that should be safer than open, though it doesn't prevent people from plugging in a cable that isn't connected to anything
 
I use this one:

https://m.ebay.co.uk/itm/220V-Solder-Smoke-Fume-Absorber-Extractor-Fan-with-5-Carbon-Sponge-Filter-Sheets/362774229216?ul_ref=https://rover.ebay.com/rover/1/710-53481-19255-0/1?ff3=2&pub=5575376664&toolid=10001&campid=5338268676&customid=EAIaIQobChMIio6UuK_b5QIVSMayCh3H6giQEAQYBSABEgIS2vD_BwE&lgeo=1&item=362774229216&srcrot=710-53481-19255-0&rvr_id=2173581059628&rvr_ts=4c891a1716e0ac3d8cd0ac37fff7a73b&_mwBanner=1&_rdt=1&ul_noapp=true&pageci=445a1ce7-55e0-4ab8-a9f3-e0a3acf2b39f

Only if I do a lot of soldering

It is not legal any more I Denmark, but those rules do not apply to my home lab

Cheers

Klaus
 
On 11/8/19 1:46 PM, whit3rd wrote:
On Friday, November 8, 2019 at 9:25:10 AM UTC-8, Alex Borroughs wrote:
I've been looking for a cheap, possibly DIY solder smoke solution.

The HEPA filter scheme is intended to trap solid particles, like pollen; fumes from soldering
are typically resin (RMA flux) or organic vapors (from a variety of alcohol-soluble
and water-soluble fluxes). A LOT of soldering is required to emit as much as
a gram of material from these sources.

For solder smoke, anything that is a solvent for those materials, should absorb efficiently,
it doesn't have to be a HEPA filter (because it can adhere-to/dissolve/trap the
chemical substances of interest, not just particles in a size range).

Get a little glycerine and spray it onto any suitable air filter medium, it'll
work on light-alcohol-soluble resin flux, and is mildly hygroscopic so will
also stick to any water-soluble droplets. Once a year, replace the dirty
filter. Or, maybe just use a mesh that can be run through the dishwasher?

https://www.mcmaster.com/reusable-air-filters
Click to expand...

Interesting. Well, the design Mr. Horton talked about used a washable
synthetic filter that had to be cut into the ovals or circles to fit
into his container. It runs about five dollars and seems to be the size
of a box fan to start with. So, spray with glycerine, place across the
fan input, and have at it I assume? That would certainly be a lot
cheaper than the HEPA's.
 
fredag den 8. november 2019 kl. 18.25.10 UTC+1 skrev Alex Borroughs:
I've been looking for a cheap, possibly DIY solder smoke solution. I
did see the device here that someone shared, but it appears to use water
and it looks like he's adding the carbon later. I had hoped for
something simpler, then I came across this:

https://www.youtube.com/watch?v=kH5APw_SLUU


My local home improvement store has this filter:

https://www.amazon.com/dp/B00TUDHPS8/ref=twister_B07YT5F24V?_encoding=UTF8&psc=1


That particular filter, although somewhat expensive (MERV=12), is
supposed to remove smoke along with a host of other pollutants. It
looks like there are one or two filters also available at even higher
MERV ratings, but more expensive and I wanted the cheapest alternative
that would still take care of the smoke. Using a filter like this in
front of the box fan and placing near my soldering area would no doubt
suck in the smoke, but what about the effectiveness? Anyone ever try it
or use this method? Also, as I wouldn't be running the combination all
the time, it should last a lot longer than 3 months.

Thanks.
Click to expand...

for smoke you probably want something with activated coal like a filters
for a ventless range hood
 
On 08/11/2019 7:05 pm, bitrex wrote:
On 11/7/19 8:34 PM, Phil Allison wrote:

--------------------

Question 2:

The same amp has a shameful design problem with the output stage.

Wilful stupidity.

Bet nobody gets it.



....  Phil




The feedback around the output transformer back to IC4 is DC coupled,
the line out jack is DC coupled too, and if the line out jack is
connected and there's a DC offset/ground potential difference on
whatever you plug it into you get a big DC offset at the output of both
the IC-4 drivers
Click to expand...

DC offset at IC4 outputs won't couple through the capacitors to do harm.

How are you going to get DC offset across the transformer exactly?

I think a problem is the shorted output transformer when no speaker
plugs are in will also short out the feedback so if there is any input
the amplifier will try its very hardest to amplify it.

piglet
 
Klaus Kragelund <klauskvik@hotmail.com> wrote:

I use this one:

https://m.ebay.co.uk/itm/220V-Solder-Smoke-Fume-Absorber-Extractor-Fan-wi
th-5-Carbon-Sponge-Filter-Sheets/362774229216?ul_ref=https://rover.ebay.c
om/rover/1/710-53481-19255-0/1?ff3=2&pub=5575376664&toolid=10001&campid=5
338268676&customid=EAIaIQobChMIio6UuK_b5QIVSMayCh3H6giQEAQYBSABEgIS2vD_Bw
E&lgeo=1&item=362774229216&srcrot=710-53481-19255-0&rvr_id=2173581059628&
rvr_ts=4c891a1716e0ac3d8cd0ac37fff7a73b&_mwBanner=1&_rdt=1&ul_noapp=true&
pageci=445a1ce7-55e0-4ab8-a9f3-e0a3acf2b39f

Only if I do a lot of soldering

It is not legal any more I Denmark, but those rules do not apply to my
home lab

Cheers

Klaus
Click to expand...

All you need is the eBay item number:

https://m.ebay.co.uk/itm/362774229216

If you really need a long url, use https://tinyurl.com/

https://tinyurl.com/y2uhbcpk
 
On 08/11/2019 9:10 pm, Phil Allison wrote:
piglet wrote:

----------------


I think a problem is the shorted output transformer when no speaker
plugs are in will also short out the feedback so if there is any input
the amplifier will try its very hardest to amplify it.



** Musos will not play for long when there is NO sound coming from the speaker.

Tubes can survive the abuse for a surprising amount of time.

Plate dissipation goes high ( may glow dull red) but that is not a cause of immediate failure.


..... Phil
Click to expand...

Ok, thanks. I am stumped now. Last deperate try: is it something like
the grid +30V rising up too quickly at switchon doing something bad
before the cathodes are hot?

piglet
 
On Friday, November 8, 2019 at 8:56:54 AM UTC-5, tabb...@gmail.com wrote:
On Friday, 8 November 2019 12:37:27 UTC, Michael Terrell wrote:

In another thread you made a comment about ';an old HP Curve Tracer. They never built any for sale. If you do some research they built one and only one for use in house by one engineer. Only one unit. It wasn't until they became Agilent that they started producing equipment to test semiconductors on the production line.

I used to have a Marconi badged sig gen that Marconi never made. It turned out to be some other mfr they had rebadged, then their evaluation rejected. It was afaik a 1 off.


NT
Click to expand...

I have a Microdyne C-band signal generator that was never sold to anyone. It was designed to use for final testing and repair of their CATV and Broadcast Satellite receivers. It may be the only surviving unit. There was no documentation in the Archives when t was given to me. The output attenuator was a $900 Weinschel variable. That was the price 20years ago. I would hate to need a new one, today.

https://www.weinschelassociates.com/store/VA05.aspx
 
On 08/11/2019 2:01 am, Phil Allison wrote:
On Friday, November 8, 2019 at 12:57:25 PM UTC+11, bitrex wrote:
On 11/7/19 8:34 PM, Phil Allison wrote:

Hi to all my loyal followers,

-----------------------------

The term "bounce" is applied when an item that has been recently repaired is brought back for a similar or repeat failure.

Mostly it's a false alarm, a new problem or just once in a while the same failure involving the new parts. This is the worst scenario and for me very rare.

One that comes to mind was a MusicMan hybrid guitar amp - the RD50. The circuit is all solid state except for a pair of 6L6GC tubes for output.

https://www.thetubestore.com/lib/thetubestore/schematics/MusicMan/Musicman-RD50A-Schematic.pdf

One came to me with the input op-amp ( IC1) having it's output stuck to a DC rail. Fitted a new TL072 and away it went, good as new. Unusual failure, but shit happens sometimes.

It was back in a week with the new IC blown, just like before.

Another TL072 fixed it again, but I smelt a big fat rat.

Since the op-amp interfaced with the external world of musicians and their assorted paraphernalia - it must had failed due to abuse, twice.

But what exactly ? To stop the nonsense, I fitted 1N4148 diodes from pin 3 to each rail as a precaution. Walter C. Jung's "IC Op-Amp Cookbook " gave support for fact that such inputs were vulnerable.

The customer was not happy, he insisted on speaking with me and was very aggressive. I had understood he was a school teacher but it turned out he was in fact a *Taekwando* instructor !!

He expected the new repair to be covered by warranty, but I was not budging.

He insisted that guitar amps were built very tough to take all sorts of abuse.

I assured him he was mistaken: "I make my living because that's not true" - I stated firmly.

After extracting a few details from him, it all became clear.

Any guess what seemingly innocent act he had performed done, twice ?


--------------------

Question 2:

The same amp has a shameful design problem with the output stage.

Wilful stupidity.

Bet nobody gets it.





He was running line-level signal from a mixer into the input, had the
line out from the amp connected to the same mixer, and accidentally
routed the output directly to the input


** Very devious thinking there.

The actual scenario is quite simple and what many musos do all the time.

Guitarists that is ...


..... Phil
Click to expand...

Do guitarists test the amp is working by touching the plug tip to get a
mains hum/buzz from the amp - that invites static discharge?

piglet
 
Michael Terrell is Nasty & Bonkers wrote:

----------------------------------------
Phil Allison wrote:

SJE = special type.

No, it isn't


** Yes it is.


Really?
Click to expand...

** Yep.

FFS "special" = non stock in some way.


That isn't what Motorola told me at a trade show.
Click to expand...

** Every "house number" power BJT I have come across WAS special.

Selected on test for Vbe, Hfe or Vce breakdown, mostly so they could be used in parallel groups with close matching.

Service info from famous makers like like Crown and Peavey warned to only use the same in repairs.


The 'S' prefix is how Motorola marked house numbered parts for customers.

** Yep, after putting them through a selection process as needed for a particular purpose. The stock number in this case was quite obscure.


Only if the customer requested it, and paid dearly for it.
Click to expand...

** It was not very expensive, Motorola returned parts that did not meet customer spec back to stock.



SJE1692s were matched for close tolerance on Vbe and Hfe.

All examples were damn near the same.



Sigh. I said, May or may not be tested for the customer.
Click to expand...

** You must be nuts - there is NO dispute here.

FFS Selected = special !!!!



In another thread you made a comment about ';an old HP Curve Tracer.



** Was not mine and I never saw the damn thing.

Could have been Tek575 or 576, not HP.

So fucking what?

In other words, you were caught in another lie
Click to expand...

** FSS, it was nearly 40 years ago, not mine and never seen by me.

You are one VILE FUCKING NUT CASE

Get cancer and fucking die.
 
Don Kuenz, KB7RPU wrote:

---------------------------

** Normal use, no unusual devices and something he had done many times.



..... Phil


The guitarist follows this ritual first, before the smashup:

1. power on the amp
2. turn the amp gain all the way up
3. turn the guitar gain all the way up
4. stand in front of the speaker and face it
5. plug the guitar into the live amp
6. turn the gain down a smidge to stop the shrieking feedback
7. if U1's still alive tune the guitar otherwise exit the ritual
8. strum the A chord
9. strum the D chord
10. strum the E chord
11. play an ascending arpeggio
12. play a descending arpeggio
13. pick through the first few bars of "Stairway to Heaven" a few times
14. Go back to standing in front of the amp and face it to create the
shrieking feedback necessary for a Hendrix state of mind.
15. play a rough rendition of the "Star Spangled Banner" once

Thank you, 73,
Click to expand...

** ROTFL !!



...... Phil
 
bitrex wrote:

------------------
DC offset at IC4 outputs won't couple through the capacitors to do harm.

No, but it will cause the amp to clip asymmetrically when the output
stage is driven hard (in the way guitarists like to do) and sound like shit
Click to expand...

** No it doesn't.

The full symmetrical cathode drive circuit you see replaces an earlier tube drive circuit that had exactly that issue.

It was however a disastrous step, helping to put the brand off the market.


...... Phil
 
On Friday, November 8, 2019 at 7:52:33 AM UTC-5, Phil Allison wrote:
Phil Allison is an asshole wrote:

-----------------------------------
Phil Allison wrote:

SJE = special type.

No, it isn't


** Yes it is.
Click to expand...

Really? That isn't what Motorola told me at a trade show. I was told that house numbering was as I said above. Back before the Internet I would see them once a year in Dayton Ohio to pick up new datasheets, Application Notes and talk with them. I needed data on some SRF RF power transistors. That was when I was told how their system worked. They were at the Dayton Hamvention each year, since most new Amateur radios models were introduced at that show. It had an attendance of about 50,000 people, for a three day event.


The 'S' prefix is how Motorola marked house numbered parts for customers.

** Yep, after putting them through a selection process as needed for a particular purpose. The stock number in this case was quite obscure.
Click to expand...

Only if the customer requested it, and paid dearly for it.

Motorola quit making transistors, two decades ago.

** The amp is a 40 years old design, as marked on the schem.
Click to expand...


SJE1692s were matched for close tolerance on Vbe and Hfe.

All examples were damn near the the same.
Click to expand...


Sigh. I said, May or may not be tested for the customer. At Cincinnati Electronics we needed some obsolete transistor to continue building the PRC77 military radio, which was a NATO design. Motorola could still make them, but they no longer had the equipment to test them, so they shipped 1100 for every 1000 ordered. Incoming inspection had to test every single transistor. NATO designs required all member nations to agree to changes, and it took years to update the BOM on equipment.
In another thread you made a comment about ';an old HP Curve Tracer.



** Was not mine and I never saw the damn thing.

Could have been Tek575 or 576, not HP.

So fucking what?
Click to expand...

In other words, you were caught in another lie about something you are totally ignorant of. There is a huge world outside of your rented squat, and it has at least a thousand times more than what you understand about Electronics. I was repairing Guitar amplifiers and PA equipment over 50 years ago, when I was 13 but I moved on to complex equipment. Things that you could never figure out how to maintain. You are just another hack.
 
mako...@yahoo.com wrote:

-----------------------------
I'm going to guess the muso would first plug his cable into the amp
and THEN plug it into the guitar.

The tip of the phone plug would touch the guitar first and couple
whatever static charge on him directly into the input of the op amp.
Click to expand...

** Close, but no banana.


....... Phil
 
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