DIY: Pass F5 turbo v2 initiated

After long gap closing on completion.

Boards populated.

Need to do wiring.

Nice, go slow and before power on don't forget to check all biasing to zero.
Best of luck.

@bhaskar, nice build. Let it working for a month then recheck the current status again. Though your heatsinks are heavy it won't be problem for you. Good!
 
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Hi all,

With lots of spoon-feeding from FM Kroyin & Om finally completed my F5T V2 built & managed to run it successfully. The cabinet & heat-sink is same as Kroyin, so obviously the look is also same. Presently running at 300mV Bias / ~3mv offset. Heatsink is reasonably cool, no problem touching at all. Here are some pics. Will arrange the wire mess B4 final box-up.


01p1020806.jpg


03p1020807.jpg


04p1020808.jpg


05p1020809.jpg


Sound wise I must say that the clarity is never heard B4. Gain/Bass was weak initially due to CNC output problem as mentioned by OM previously. So added SSP and now bass is good enough as per my liking(kindly remember that my ears are used to the very bass heavy sound of Sansui AU-719, which will take little time to wear off:)). Slowly it's opening up nicely(almost 20 hrs running time till now). What is worth mentioning that at a medium to low volume the reproduction is excellent. Let's hope it gets better & better as time passes.

Finally thanks again to all forum members who made this GB/built a great success with obvious special mention of Om, Sachin & Krishnendu(Kroyin).

Best regards,

Bhaskar
Nice Monoblocks sir.I am happy you liked it.

Regards,
Sachin
 
@bhaskar, nice build. Let it working for a month then recheck the current status again. Though your heatsinks are heavy it won't be problem for you. Good!

Noted and thanks again for the advice. Meanwhile let the amp burn in while we enjoy music all the way.

Bhaskar
 
Nice Monoblocks sir.I am happy you liked it.

Regards,
Sachin

Better to call them mono'towers' instead of monoblocks.:):) And I'm really happy making it. Remember the phone conversations which is possibly one of the reasons of this GB. Thanks to you & Om again for making this possible.

Bhaskar
 
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Better to call them mono'towers' instead of monoblocks.:):) And I'm really happy making it. Remember the phone conversations which is possibly one of the reasons of this GB. Thanks to you & Om again for making this possible.

Bhaskar
Yes I do remember you said "F5 to banana hi hai" after listening Kroyin's F5 first time.That started the whole thing.

Regards,
Sachin
 
Switching the F5T on

This is what I plan to do. Let me know if I need to do anything extra.

Set the both pots of each amp to 0. This can be acheived by connecting a DMM across 1K resistor near to the pot.


1. Use the light bulb tester in series. Make sure it glows low initially then increases its intensity.

2. Remove the light bulb tester. Remove the connection from psu to amp boards. Check the voltages at the PSUs between +ve and gnd and -ve gnd on the psu boards. They should read about 32 volts approx.

3. Connect back the psu to the amp slowly set the bias using 1/2 turn intervals. Use two DMMs one on the source resistor and other on the output terminals. After every turn on one side of the amp, there will be dc voltage reported at output terminals. By turning the other pot the dc voltage needs to be got down to nearby 0.

after 300 mv is read on the source resistor dmm then stop it and put the lid on. Check the dc voltage at the terminal after an hour. Also check the temperature of the heat sinks. We should be able to keep the hands on the heat sinks for at least 5 secs. Bias can be increased or decreased based on the temperature of the heat sinks.

With regards to the connections from the amp board

1. Speaker out goes to Red terminal of speaker out.

2. The PGND which is right below the speaker out in the center goes to the black terminal on the cabinet.

3. +ve, -ve and pgnd 2 go to psu board.

4. RCA input needs to be soldered in
 
Switching the F5T on

With regards to the connections from the amp board

1. Speaker out goes to Red terminal of speaker out.

2. The PGND which is right below the speaker out in the center goes to the black terminal on the cabinet.

3. +ve, -ve and pgnd 2 go to psu board.

4. RCA input needs to be soldered in

You are correct Pandu.

Here are steps -

Start with all disconnected - transformers, Rectifier Board, PS filter and F5 turbo Amp boards.
Connect them one by one, step by step after power down and disconnecting mains from wall. No hurry, its result day of long preperation and hardwork.


1. Mains Supply (Caution: This is deadly, be careful)
Checking:
Check mains wire to switch, through fuse and transformers. Output wires (secondaries) of transformers are taped and secured for avoiding short circuit.

Mains wire - live (L) must not short to chassis, neutral(N) and earth ground(E).

Connect as below and then power ON:
Connect primary of each transformer and use >200VAC range on DMM to check output voltage on secondary. If measures 24V then move ahead.

Power off and disconnect mains wire.

Connect 100W bulb tester in series of mains (L) Live wire and proceed.

2. Rectifer Board:
Checking:
PCB copper, heatsink of diodes is not shorted to any wire, chassis or any metal nut-bolt. Verify all [~] marked pins are not shorted to [+] and [-] marked pins. Also [+] and [-] not shorted to each other.

Connect as below and then power ON:
Connect all secondary pairs from transformer to AC input points on the PCB and power on.

Light bulb on mains (L) wire should flash for moment and goes off.

Change DMM to DC 200V range.
Measure voltage on [+] and [-] point of rectifier board. If its 34-35V then move on. You are correct till this point.

Power off and disconnect mains wire.

3. Filter board:
Checking:
Verify all pins of +V and -V are well isolated from mounting nut-bolts and chassis. Polarity of bigger caps are in correct direction, matching with supply output polarity.

Connect as below and then power ON:
Connect 4 X ([+] & [-]) from rectifer to PS filter board.
After power ON Light bulb on mains (L) wire should flash for moment and goes off. If keeps glowing then disconnect power immediately.

Keep DMM to DC 200V range. Measure output voltage wrt GND toward output of PS filter board. Unloaded voltage 34-35VDC.

Power off and disconnect mains wire. Wait for caps to discharge for 5 min.

4. Each amplifier board:
Checking:
  • Check MOSFETs are well seated onto their heatsink and tightly attached to heatsink through mica and paste. No air gap in between mating surfaces of MOSFET and heatsink.
  • PCB is well secured and part leads are not touching to heatsink.
  • Input and output wire are not shorting to anywhere except intended connectors - input (RCA - PCB ) and output (Banana post - PCB).
  • Those green NTC are touching MOSFET body and stable. You can put little heat paste between their body contact points.
Important: Change DMM to 2K? range.
Verify 0 resistance across each 1K? resistance near 5K? trimpot P1, P2. You will listen clicking sound from trimpots, you have to stop turning its screw. Mark the direction of turning screw (-) in which you made its resistance zero. That way you made bias also zero. Remember opposite direction is +ve. Mark it if possible. User marker pen. You are ready to go.

Connect PS wire with correct polarity and verify.

Powering on:
DMM batteries are new and leads are okay, not loosely connected.

Connect DMM with mV range to source resistors at extreme. You can use 2 DMM (if possible) each on P-side and N-side. No problem with having only one on either side. Use other DMM on output with mV range.

After power ON Light bulb on mains (L) wire should flash for moment and goes off. If keeps glowing then disconnect power immediately. Also if you see high voltage or max(1 . ) in any of DMM then stop, disconnect power immediately.

If you are okay till this point then power off mains, remove light bulb tester and continue henceforth.

Biasing:
Now turn half rotation in +ve direction each time in each side till you see measurement in any of DMM. Hence forth turn half rotation at one side of preset and null output to zero mV by setting other side of preset.

Settle at 100mV across source resistance, let it settle for 1 hr. Take a break. Observe heatsink and MOSFET body temperature, both are passing 10sec touch test.

Repeat above step till 200mV and again wait-check for 1 hr.

Same way till 300mV.... till 375mV ( that's my limit, your limit is till heatsink pass 10sec hand touch test)

After it is stable, cover the top plate and wait for another 1-2 hrs. Observe output offset and source voltage. If all stable then you are done.

For -ve offset rotate (-) side trimpot in (-) direction, for +ve output offset rotate (-) side trimpot in (+) direction. If voltage across source resistor increases ( that means bias increased) then decrease both trimpot gradually in opposite direction you increased.

Best of Luck!
 
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Anilva

thanks for pointing out my misconception.

Today I started wiring and testing.

Test Number 1. Check the voltage across the secondaries. they are all 26 v.

Tommorrow plan to test the psu output voltage. and then may be the amps.

One question.

Whole time I had the bulb connected in series while testing the voltage across secondaries. I am not sure what is the reason but the bulb did not glow at all.

Should I have teh bulb in series when testing the psu output too.

Let me know.

Thanks
Pandu
 
One question.

Whole time I had the bulb connected in series while testing the voltage across secondaries. I am not sure what is the reason but the bulb did not glow at all.

Should I have teh bulb in series when testing the psu output too.

Let me know.

Thanks
Pandu

Bulb will not glow as there is no current draw from the transformer barring minimal one. Only when you connect the bridge rectifier and the capacitor bank, the light will glow bright to begin with as the power supply starts drawing current for charging the capacitors. Once the capacitors are charged, the power supply draw becomes near zero and the bulb will go off.

If there is a short or any other fault, the power supply draws current and the bulb will continuously light indicating a fault. You should switch off and start debugging the problem.

Be careful: The capacitors will be charged fully and discharge huge amount of amps if touched. You need to have a bleeder resistor (which is on Om's PCB) to slowly discharge them to zero before you touch.

Cheers.
 
hello all,
does anybody know where in india i could find the following JFETs used in the F5 ckt ?
-2sk170
-2sj74

or can someone suggest equivalent complementary pairs .
Thanks:)
 
hello all,
does anybody know where in india i could find the following JFETs used in the F5 ckt ?
-2sk170
-2sj74

or can someone suggest equivalent complementary pairs .
Thanks:)

You will not get them in India nor there are decent equivalents which are available in India. You need to buy them from spencer or alweit. Both their coordinates are available on diyaudio.
 
Got it done.

Wow!! DOne it.

First of I need to thank, Hifivision members especially Om, Anilva, sachin. Also need to thank my wife and my daughters for bearing with me. I had dissappeared from my family during my cabinet build days and last two weeks have been really hectic. Being a first time DIYer, Very in efficient too much apprehensive and too much checking before doing anything.

Om,

Special thanks for taking my calls. Must have called you hundreds of times.
atleast for me you are a dictionary. You had answer for everything I threw at you.

Without the GB, My F5T would not have happened. Special thanks to Om and sachin.


After countless number of hours of research, connecting tens of wires, soldering hundreds of parts, reading thousands of posts in diyaudio Finally I am done with my F5T v2.

How does it sound. Nice. I have not connected it to my main paradigm S4 speakers. Currently running energy take 5 which in fact surprisingly sounding nice. F5T is little too much for my Take 5 speakers. I had earlier run them using yamaha AVR many moons ago.

I had biased it for 370 mv with no fan on in the room. I have bought it down to 320 mv as I write. I need to check the other channel.


Speaker level dc output is varying between 30mv thru -30mv. I am not sure what is the acceptable level of dc offset.

Pictures comming soon.
 
Pdhanwada, this is great news. Congratulations! Welcome to Pass club.
Thank you very much for your kind words. You are inspiration for us. First DIY doing with F5t is achievement. Now we are waiting for pics. I hope you will like pass sound.

PS: I started my build. Took inspiration from you.
 
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Re: Got it done.

Speaker level dc output is varying between 30mv thru -30mv. I am not sure what is the acceptable level of dc offset.

Congratulations. Frankly this is beyond the realm of any first time DIYer and you seem to have succeeded with adequate support from Om as mentioned by you.

Ideally the offset should be adjusted for '0' mV. You need not bias both the legs of the amp for the same bias level. All you have to do is bias one of the legs to 320mV or whatever you choose and make sure the other leg is adjusted to give you 0 mV at the output. Ofcourse while doing this you need to adjust each of the sides incrementally.

IIRC, Pass had indicated that drift upto 70mV is OK in his original F5 article.

Cheers.
 
Agree I am first time diyer. Without the forum support couldnot have done. This also proves that the forum is so good for newcomers.

Right now bias is changing between 318 mv to 325 mv. Dc offset has also got within 15 mv.

Finally I got to run the Amp thru my Paradigm signature speakers. There is huge difference on the Bass side of the frequency. I get a feel that my older speakers have been replaced by big floorstanders. Compared to my previous amp I need to run this at 6 to 8 db higher. My previous amp had a gain of 28 where as this is 22. This is not an issue.

I think I did the right thing by picking up f5T rather than F5. Gain could have been an issue on F5.

Thanks
pandu
 
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