DIY mini T2 Build Thread

[jamesmking]

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Edited March 31, 2021 by jamesmking

[jamesmking]

22 hours ago, chinsettawong said:

Wow!  I tried to solder some SMD resistors today using solder paste and hot air.  It’s so difficult!  I turned the air down to the minimum already, but as soon as the solder started to melt the resistor got blown away.  Is there any good tip for a beginner?

I did some experimentation and found that low airflow and fairly high air temp worked best for me.

I have a quick 861dw hot air station. I set the airflow to 5 out of 120 and set to 360C (the temperature will depend on your solder paste melting point). I hold the hot air nozzle with one hand and with the other I use tweezers to keep the smd part in place. If you do not hold the part in place almost any airflow will send components into low earth orbit. The tweezers I use are curved on the end which makes it easier to place components, keep your hands away from the heat and easier to see what's going on.

 

Edited April 1, 2021 by jamesmking

[JoaMat]

I always do smd soldering with fin tip solder iron and after a long time of practicing I feel quite comfortable with that. I’ve tested with hot air station and with proper amount of solder paste on the pads and when using low air flow I managed to solder without components blowing away. And it’s a nice feeling seeing a component nicely aligning up on its pads.  But I prefer the soldering iron technique. Me and solder paste don’t mix well. After a while the whole table is a mess and I even have solder paste on my nose.

With some practice I’m sure everyone can do smd soldering, but it can be very frustrating initially. 

[Kerry]

I use an oven (when it’s not too cold outside) and a hot air station during the winter. 

I agree that you need to set the air velocity way down.  I do keep a tweezers handy in case something moves or tombstones, but I generally don’t need it. 

Try to have the air gun directly over and perpendicular to the parts. I move it around in small circular motions anywhere from 12mm - 25mm above the parts. 

It’s very important that the parts are somewhat centered in the pads. For 0603 and down, I use a loop while I’m placing the parts. 

Once you get the hang of it, it’s a very fast way of soldering. 

[mwl168]

To date I've soldered all the SMD applications using a fine-tip soldering iron and a fine tip tweezer. I also find using very small gauge solder is key - I use .02"/3mm diameter solder from Kester with 2% silver and it works great. You can get a small tube of this solder from Mouser offered by NTE. I can try dig out the part number if you are interested.

I want to experiment with a hot air station but have not done so yet. Mostly because I could to decide how much to spend and which one to get. Even the very basic one from the trusted brand (JBC, Hakko, etc.) costs an arm and a leg. 

Edited April 1, 2021 by mwl168

[jamesmking]

15 minutes ago, mwl168 said:

To date I've soldered all the SMD applications using a fine-tip soldering iron and a fine tip tweezer. I also find using very small gauge solder is key - I use .02"/3mm diameter solder from Kester with 2% silver and it works great. You can get a small tube of this solder from Mouser offered by NTE. I can try dig out the part number if you are interested.

I want to experiment with a hot air station but have not done so yet. Mostly because I could to decide how much to spend and which one to get. Even the very basic one from the trusted brand (JBC, Hakko, etc.) costs an arm and a leg. 

the quick 861dw comes highly recommended 

 

 

 

its also useful for drying out pcbs after ultrasonic cleaning, removing surface mount components, heat shrink etc.

 

 

[Pars]

Michael,

Check out the Rossman group videos on YouTube. He does a review of some hot air stations. He likes the Quick, but I believe he has one from Atten which is cheaper and performs just as well.

 

[chinsettawong]

Thanks for all the good advices.  I change the air nozzle to a bigger one so that it has slower air velocity, and set the temperature to a bit higher, and now it goes a lot better.  

I still have a long way to go though.

By the way, the smell of the flux is really bad.  Do you guys wear a mask or use a filter fan when doing the hot air soldering?  

 

Edited April 1, 2021 by chinsettawong

[starcat]

On 4/8/2020 at 5:45 PM, JoaMat said:

Now when Kerry regulators and psu board are on its way I and maybe a few other builders wonder what transformers might be appropriate.

Will Kerry publish his new mini T2 PSU? That would be awesome!

[Kerry]

There was a group buy for this already. You should be able to find what you need there

[starcat]

16 hours ago, Kerry said:

There was a group buy for this already. You should be able to find what you need there

Hey Kerry, I have typed this wrong. I know the GRHV/LV from within the mini T2, I was thinking about your later and scaled down real T2 PSU. 

[Kerry]

I don't have a scaled down T2 PSU.  The one I use is based on the original T2 PSU schematic.

I am working on a golden reference version, but that project is not completed.

Once upon a time, I did a golden reference version, but it was too fragile.  In my new project, I will add current limiters in front of the regulators, like Kevin did in the T2 PSU.

[Eskamobob1]

Hey guys. New and utterly uneducated on electrical engineering. Is the mini T2 a shrunk version of the T2 or a new design just based on the t2 topology? I have been drooling over a t2 for ages but have some space tight constraints (mostly footprint) and most of this thread has been over my head so I couldn't figure out the answer 

[jamesmking]

joamats mini t2 with golden reference psu only uses modern and available components. The amp boards are mostly surface mount and the components are fairly tightly packed. Its based on the t2 topology but simplified and runs at lower voltages and has less voltage rails, no virtual batteries and less current sources. The mini t2 still requires a fair bit of space. I got the amp boards, and the three golden reference high voltage power supplies, the high voltage delay board and low voltage power supplies in a 2U case 400mm deep. The mains transformers had to go in a separate case... So even the mini t2 might be too big for you. Although you could make the main amp smaller by putting the power supply pcbs in the same case as the transformers. I don't think you could fit everything into a single 2u case 400mm deep.

Both the original and mostly modern t2s are gigantic partly due to the many different psu rails and the considerable number of constant current sources on the amp boards. I had to make the amp board smaller just to fit it in a 2u 400 deep case and the many psu pcbs and transformers had to go into another 2u 400mm case... My T2 is twice the size of my main systems power amp!

The original diy t2 uses many transistors that have been unavailable for many years and so are expensive and difficult to source. the markets are also flooded with fakes which will almost certainly fail on first start-up

the mostly modern t2 requires a few out of production transistors.

Its possible to build an entire blue hawaii with golden reference low and high voltage supplies in a single 2u 400mm case. So if space is a real issue that might be an option for you and the later versions only use modern components and is a much simpler and cheaper build than a full t2.

 

[micon21]

Hello. A huge request to those who have done a miniТ2.
I am interested in the parameters of the TOR transformer. how many volts at the output and the current strength 

[JoaMat]

On 2/7/2022 at 10:57 AM, micon21 said:

Hello. A huge request to those who have done a miniТ2.
I am interested in the parameters of the TOR transformer. how many volts at the output and the current strength 

There are some posts on this subject on page 4 this thread.

[micon21]

I looked it up, the transformers are approximately clear. thank you. 
I do not see in this thread the circuit diagram of the power supply for the mini.

 

 

 

 

[MLA]

Check the GRHV thread and files (James listed all flavours some time ago).

[micon21]

On 2/9/2022 at 7:54 AM, MLA said:

Check the GRHV thread and files (James listed all flavours some time ago).

I looked. I saw two diagrams, but it is not clear to me which variant is intended for mini T2.  
And it is not clear why the mini variant is not in the topic of mini T2.

[jamesmking]

On 2/8/2022 at 11:20 PM, micon21 said:

I looked it up, the transformers are approximately clear. thank you. 
I do not see in this thread the circuit diagram of the power supply for the mini.

 

 

 

 

there are many possibilities:

for the power supplies first you need to decide if you want to heat the valves up before you apply high voltage.

If you do then there are two options. Do you want to implement the delay using a relay (and either switching the ac input to the high voltage transformer or dc output of the high voltage psus) or apply a dc voltage to switch on the high voltage psus?

IF you do not want high voltage delay or want to do the entire delay e.g. by timed relay off the psu board then use the golden reference 1.7 series psus

if you want to switch on the hv psu by providing timed dc then use the golden reference 1.8 boards.

next you need 3 hv rails - two positive (220V and 400V) and one negative (-460V). So you need to look at the options.

golden reference Dual boards have a positive and negative rail, headphones bias and a simple low voltages + and - rail  on one pcb but are of course wider than a single rail board.

 

or you could go for three single rail separate golden reference boards. boards with left in their name have a negative rail and simple low voltage supplies. boards with right in their name have a positive hv rail and the 580V headphones bias.

See https://www.head-case.org/forums/topic/15634-goldenreference-high-voltage-power-supply-grhv/#comment-851207

for board physical sizes.

Next for an over kill design you may want to have a high performance low voltage section using a golden reference LV board instead of the basic low voltage section provided on the golden reference hv boards. The low voltage provides power to the dc servo, balance servo and cathodes of the 6922s that the input signal goes into

for the delay board you can use https://drive.google.com/drive/folders/1r3g2TAtBUaBdiMorTWX7yYgeJ7maQbYW

 

or use what I use which is taken from a German website:

schematic:

http://www.high-amp.de/html/reg_pws_v3_add_on_schematics.html

gerbers etc

http://www.high-amp.de/powersupply_stabil_add_on.rar

NOTE the hi amp delay board also provides a dc 6.3V supply capable of powering the 6922s but then requires 2 windings of about 8VAC rms as its input. Or you can just not implement the circuit for the 6Vdc heater supply and run the delay timer and relay off a single 6.6VAC winding without issue - which is what I do (see bellow). If you only implement the delay from the high amp board this is the schematic of what you need:

 

Here is my build with a golden reference HV 1.7 dual and golden reference 1.7 right (modified by me to remove the bias components), and a golden reference lv

(the delay board is in the psu box with transformers.). The delay board I designed myself based upon the delay circuit from high-amp. It runs off one of the 6922 heaters and is modified so it switches all three outputs of the HV transformer - which is why there are two relays. It also provides screw terminals so you can attach dropper resistors if your heater voltages are two high. (I like to run the heaters 6922s at 6VAC rms). The delay board I made also provides dc power for the led in the on off switch. Removing the fuse allows you to power up the heaters and low voltages only.

The standard hi amp delay board only provides a single relay which can be used to switch the AC input to the high voltage transformer. This mandates the use of two transformers - one for the low voltages, heaters and delay board power and a separate one for the high voltages.

My board switches the outputs of the HV transformer and so could be used with a single transformer setup or dual transformers.

It also provides terminals for all voltages going to the amp. (I have a build policy that all pcbs and major components e.g. transformers should be removable for servicing with zero disordering - hence the screw terminals added to the delay board.)

 

here is the gerbers for my dual relay pcb with screw terminals:

mini t2 delay with screw terminals.zip

 

here are the gerbers for the dual delay with no extra screw terminals for the other voltages:

 

 

mini t2 dual relay delay no screw terminals.zip

 

 

Edited February 12, 2022 by jamesmking

[micon21]

Оgo!  
You surprised me, it turns out that the power supply has many functions.  
I would like to thank you very much for the explanation, of course it is necessary to study and try to understand the developers' ideas.

[micon21]

Sorry, What is it? 
I hover the cursor, a link appears, but nothing opens. I tried it on different browsers, but nothing opens.

[Pars]

They work for me. Click on the file icon and a zip file can either be opened or downloaded.

 

Edited February 14, 2022 by Pars

[micon21]

jamesmking,      sorry. 

I understand +400v and -460v. What I don't understand is where does +220v come from?

[jamesmking]

7 hours ago, micon21 said:

jamesmking,      sorry. 

I understand +400v and -460v. What I don't understand is where does +220v come from?

+400 and -460 come from the dual golden reference board, +220V comes from the single golden reference board. 

look at the amp photo above the dual golden reference is the large square black pcb, the 220V golden reference is on the right hand side of that the blue long slim pcb. The high voltage transformer provides 3 windings, one for each of the high voltage outputs. One wire from each of the high voltage windings is switched by the long thin green delay board in the psu case. 

if you look at the right hand side transformer that is the high voltage transformer. the colour coding on the transformer wires  was green for the 220VDC supply, yellow/orange for the 400V dc supply and red for the 460V supply. 

To set the outputs of a golden reference hv board you need to change 2 resistors for each output. check the golden reference hv thread for more details.

(The 580V bias supply for the headphones is generated from the plus 400V supply.)

 

Edited February 15, 2022 by jamesmking