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F5Turbo Illustrated Build Guide
F5Turbo Illustrated Build Guide
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Old 3rd December 2017, 10:52 AM   #331
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Keremito View Post
Hello all. Thank you for all the resources I am happy to report that I have completed building the amplifier, I'm new to the forum and this is my first day project. I wasn't hesitant to do it until a fellow member decided to sell an incomplete kit.
Build when fairly well. Lots of time spent, learned a lot. Thank you for all the insight and advice find in the board.
Here are the q's.
.I'm using the 5u deluxe chassis, dual transformers at 300VA each, dual power supplies each channel gets its own+/-, rails are at +/- 40 volts using the PS3 boards and 60,000 uF of filtering per power supply side for a total of 240,000 uF. Bias set at 350 mV and 360 mV across source resistor. Output dissipation estimated just below 30 Watts per device. Differential temperature between room and heatsinks is 25 degrees Celsius. Room at 17 degrees, heatsink at 42 degrees.
If your summer temperature went up to 30degrees C (no air con), then your sink would be @ 55degrees C. This is OK.
Quote:
1. How close am I to the limit of the chassis dissipation capability?
You are getting close to chassis/sink limit if your max Ta is around 30degreesC.
Quote:
2. How to figure case temperature of the output devices? In have infrared thermometer?
If you predict rather than measure the impossible, you will get closer. For an Rth c-s of 1C/W and 30W passing across the insulator, then Tc=Ts+1C/W*30C
If you use a much more thermally conductive insulator say 0.3C/W, then Tc = Ts + 0.3C/W*30C
This better insulator allows the devices to operate 21C degrees cooler.
Quote:
3. How do I figure the maximal output, I have 8r dummy resistor 500w available and a function generator?
Don't figure it out. Measure it.
You need a scope to monitor the highest available output voltage without any sign of clipping of that signal when the load is connected. You need a fairly clean signal source <0.5% sine distortion is probably good enough.
You need an AC voltmeter that reads to better than +-1%.
You need some form of switching arrangement to prevent overheating while you take the measurements and monitor the non clipping, while driving enormous current into your dummy load.
Pmax = Vac^2 / Rload
Quote:
4. How important to balance gain between channels?
Not important. +-5% resistors (gold stripe) give a worst case error of +10% and -10% between the channels and that accounts for only 1.7dB between the channels. You can check your resistors with your ohms function on your DMM and get channel matching to much better than +-1%, giving <<0.5dB between channels.
Quote:
5. Practical way to adjust p3 if audio analyzer is not available?
Don't adjust p3. Set it exactly to electrical middle. And leave it there. Don't try to fiddle by ear. Ears+brain are terrible at measuring.
Quote:
6. Unrelated. I'm feeding the amp with a mesmerized B1 buffer without chassis ground is floating. I get a ground loop when connected, amp is dead quiet so it's the buffer. What is the proper way to ground the B1 beard?
Thank you again for everything.
It's probably not the Buffer.
Read D.Joffe and install HBRR+HBRL
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Last edited by AndrewT; 3rd December 2017 at 10:56 AM.
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Old 3rd December 2017, 06:10 PM   #332
Keremito is offline Keremito  United States
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Default F5T V2 running, have a fewe of q's to finish settings.

Read D.Joffe and install HBRR+HBRL[/QUOTE]

Thank you Andrew, I appreciate the time you took to reply. I have read a lot of your postings because they have a lot of useful technical details.
Pardon my ignorance, who is D Joffe and what HBRR and HBRL stands for? I have searched and came empty. Thank you!
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Old 3rd December 2017, 07:35 PM   #333
Keremito is offline Keremito  United States
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Default F5T V2 Pictures

Inspired by of all of you, I purchased an unfinished kit from fellow board member in Utah with most of the parts for V3 monoblocks. Thank you!. I did not have the time and skills to engineer my own chassis so I used the 5U from the store. Once I received the chassis and realized how big they are, I decided to build a V2 with dual power supplies instead. So here it is. Standard build following Jim's guide.
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Old 3rd December 2017, 08:39 PM   #334
Keremito is offline Keremito  United States
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Default F5T V2 ground loop

It's probably not the Buffer.
Read D.Joffe and install HBRR+HBRL[/QUOTE]

Andrew, I found it: Ground Loop again
Post # 22.
Thanks.
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Old 3rd February 2018, 05:57 AM   #335
joesch1999 is offline joesch1999  United States
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Default Class A

this is my first class a build, I have the amp about ready to fire up, I have the pots set to zero, my question is the fets are reading 96 ohms, is this normal for class a? on ab 400 to 500 is normal is why I ask
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Old 3rd February 2018, 07:49 AM   #336
Zen Mod is offline Zen Mod  Serbia
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F5Turbo Illustrated Build Guide
ever found anything about JFets matching ?

if in doubt , test

and , always be precise when typing ; only you know for sure what you are actually thinking ........ others can just guess , more or less
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Old 3rd February 2018, 07:21 PM   #337
joesch1999 is offline joesch1999  United States
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Sorry was late last night, when I test the legs of the transistors after installing the jumpers as explained if not cascading, I am getting readings of 96 ohms across the legs of the 9240's
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Old 3rd February 2018, 11:36 PM   #338
Keremito is offline Keremito  United States
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I would recommend to double check your work, if all is looks ok, follow Jim's (6l6) procedure to turn it on using a Variac or the Light bulb cord. One channel with be conducting a little (P-channel I think), the other will be off but it will come alive as you start adjusting the bias potentiometers. Measuring resistance will not give you a certain answer if the amp is ok. Good luck.
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Old 4th February 2018, 02:37 AM   #339
joesch1999 is offline joesch1999  United States
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Default Newbie Question speaker output

On the f 5 turbo where do you hook the speaker outputs to? I assume ve- and op but not sure, please help lol
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Old 4th February 2018, 03:28 AM   #340
Keremito is offline Keremito  United States
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Red or + post connects to O/P, black or - post connects to G (audio ground) See post #1. There is a picture showing the connection. After the schematic is picture # 14 before "power supply" picture titled "final connections"
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