I would think the Kontact stuff that soren linked to would work fine.

I can't speak directly about the Kontact stuff but my luck with "flux removers" in general was very poor until I tried simple 90+% isopropyl alcohol.  I think the alcohol was cheaper too.

1 hour ago, Pars said:

I would think the Kontact stuff that soren linked to would work fine.

It may very well be fine.

Though my experience is if the contents are not stated then it’s usually a weaker mix. It’ll still work, but not as effectively as a 98 -99% isopropyl alcohol.

9 hours ago, n_maher said:

Get the purest isopropyl alcohol that you can find in a decent quantity and several sacrificial tooth brushes.  Lather, rinse, repeat until clean.  Manage the waste appropriately.

What should I rinse with?

I've been using a semi-sharp pin to scrap off the hardened flux followed by scrubbing with a tooth brush and high purity isopropyl alcohol (90% IIRC). This cleans the flux well but tends to leave a film of residue that is viible under certain lighting conditions. 

Edited November 24, 201510 yr by mwl168

The residue is a film of fine flux, broken down by the alcohol. You may need to do several applications with the alcohol before the board becomes squeaky clean, but the isopropyl alcohol is all you need.

Each application needs a fresh batch of alcohol and the toothbrush needs a good rinse in between applications, unless you have several clean fresh ones. I'm fairly liberal and use a good amount with each pass.

I generally wipe down my circuit boards with a paper towel between scrubbings.  Otherwise, you are just rearranging the residue that's on the board. I have not been able to find the high purity (98/99%) stuff, but find that 90% works just fine.  I also give it a shot with my compressor when finished but don't think this is really a necessary step.

Me

 

 

 

2 hours ago, johnwmclean said:

The residue is a film of fine flux, broken down by the alcohol. You may need to do several applications with the alcohol before the board becomes squeaky clean, but the isopropyl alcohol is all you need.

Each application needs a fresh batch of alcohol and the toothbrush needs a good rinse in between applications, unless you have several clean fresh ones. I'm fairly liberal and use a good amount with each pass.

 

2 minutes ago, muskyhuntr said:

I generally wipe down my circuit boards with a paper towel between scrubbings.  Otherwise, you are just rearranging the residue that's on the board. I have not been able to find the high purity (98/99%) stuff, but find that 90% works just fine.  I also give it a shot with my compressor when finished but don't think this is really a necessary step.

Me

the "Kontakt Chemie" stuff is about 50% IPA.
The Kontakt Chemie seems to work ok, but needs, as McLean mentioned, 

There seems to be consensus that the proper way to remove flux residue is a combination of very clean IPA >99%  and some brushing.

My concern is, as "muskyhuntr" says: "Otherwise, you are just rearranging the residue that's on the board" ... some has suggested rinsing using deionized water and blowing off with a heat gun.

 

I use this: http://www.amazon.com/gp/product/B004SPJP5O, supposedly 99.9% isopropyl alcohol. It takes several rounds of scrubbing and drying to get boards clean enough.

Birgir posted on the T2 thread that he uses Electrolube Safewash 2000, but I haven't yet found it in the US.

Edited November 24, 201510 yr by gepardcv

2 hours ago, gepardcv said:

I use this: http://www.amazon.com/gp/product/B004SPJP5O, supposedly 99.9% isopropyl alcohol. It takes several rounds of scrubbing and drying to get boards clean enough.

Birgir posted on the T2 thread that he uses Electrolube Safewash 2000, but I haven't yet found it in the US.

Thanks, found it here:

On 29/10/2015 21.10.19, spritzer said:

Minimum 18AWG for the heaters.  Those current limits are free air and at serious loss.  You don't want that in a 6.3V heater line. 

I used 1000V rated SPC wire that I twisted and then insulated all the pins on the plugs with 600V heatshrink.  I hate doing this though which is why I'm trying my best to cram a Megatron into a single chassis... 

For the flux I use a foam cleaner from Elecrolube.  Spray it on the boards and let it sit for a minute or two.  Then brush them and then rinse under a running tap.  Let them sit for a couple of days to dry. 

from the SDS it seems to contain  AMINOETHANOL and  ALKYLBENZENE ... the latter is known to be carcinogenic ...

I guess for amateur use the >99% isoprophanol + rinsing in deionized water is a better way of cleaning the pcbs in comparison to the Electrolube stuff

Edited November 24, 201510 yr by sorenb

The amp was up and kept running 4hrs/day for 2 weeks. This amp is indeed very good. Being dynamic, detailed, and a bit of "tubby" sound, I like it very much.

BTW, I some times wonder if it's possible to use the new-designed KT family as the output stage. BH use EL34 as triode. Though EL34 is pentrode and KT77 is beam tetrode, I thought they were almost identical(working). The new-designed KT120 or KT150 can handle a little bit higher voltage and much bigger current output. So if it's possible to use KT120/150 as output stage, maybe there's no need to use current amplification like ciclotron? 

Plus, using dht tube like 300B/845 may have humming problem. So maybe using KT family is better?(though the voltage is lower....)

There is a lot more to this than simply what the tubes voltage rating is.  A lot more... 

kt120 and kt150 would work great in the megatron circuit, possibly at higher currents.

a kgst would need an additional buffer to drive the grid correctly, and a much bigger current source.

I am not talking about modifying KGST.

I was just thinking the output stage of BH=T2, and have been designed for over 20 years. KT150 was produced since 2010 as I know. Don't know about KT120. Maybe those will make a better output stage?

How does those KTs compared to dht like 845? Even though 845 still has some NOS available, the cost is insane for a matched quad. The price are at same level for modern 845 and KT120.

 

those tubes are really designed for lower voltages and much higher currents.

So for a push pull speaker amp, great for lots of power, a single pair is probably good for almost 200 watts with the right transformer.

But for a BH, where you really need 800 volts or more (can actually go to 900 these days) not a great idea

DHT's are pretty much incompatible with this and why would you want to use them, just look at the graph for a triode connected EL34.  All the later power tubes were just moar power and don't like high voltage at all. 

4 hours ago, spritzer said:

DHT's are pretty much incompatible with this and why would you want to use them, just look at the graph for a triode connected EL34.  All the later power tubes were just moar power and don't like high voltage at all. 

OK I got it. I was just thinking if it;s possible to make good use of those later tubes given the much moar power.

It seems if we want to go higher voltage in tubes then old RF tubes will be the better choice?

Now we would just use the SiT's if we want more voltage.  Less hassle and better performance. 

If we were to stay with tubes then there are few options but most are rare tetrode/pentode small transmitting tubes. 

I wanted to redo this as a single 4 layer board.  The board is 111mm x 150mm.  I'm pretty happy.  Should have it back pretty soon and will give it a go.

It supports a couple of styles of the servo for the offset so I can play a bit.

That makes my KGST look like a beast in comparison. Very cool. Any plans to shrink the PSU as well?

Wow!

Nice work, Kerry!

The AC wire for tubes seems to be a little bit too long, and close to signal pathway. Maybe remove them and just do the point-to-point wiring?

Very interesting Kerry - looking forward to seeing the finished board!

 

//UFN

Neat! Looks like there's more than a few hours gone into that. As UFN said, looking forward to the finished item.

7 hours ago, joehpj said:

Nice work, Kerry!

The AC wire for tubes seems to be a little bit too long, and close to signal pathway. Maybe remove them and just do the point-to-point wiring?

On my first version I did the heater wiring off board.  I wanted to get it on the board this time.  I used the 4 layers so that there would be a solid ground plane under the heaters and between any signal / voltage traces.  I also made sure there was some ground plane on top between the heater and servo which at worst would introduce common mode noise.

I don't think the heaters will be a problem.  They are in the signal path anyway (well sort of).