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Refurbing an old school classic Precision Power PPI Art Series A404


Wicks

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Time to refurb another old school classic. :D

This is a Precision Power (PPI) Art Series A404 and in really good condition considering it's close to 20 years old. :o

PPIA404_zps308582e5.jpg

PPI Specs:

4-Channel Model: A404.2
Continuous Power Output per Channel, x 4 Stereo, x2 Bridged
4 Ohms, 11-15 VDC, Stereo: 50 Watts
2 Ohms, 11-15 VDC, Stereo: 100 Watts
4 Ohms, 11-15 VDC, Bridged: 200 Watts
Power Fuse: 50 Amp
Dimensions (inches): 2x9.25x13"
Shipping Weight: 8.5 lbs.

Gave it a test run to see how it would perform before the refurb.

Voltage swing (unloaded) on the front right output: About 15.7 Vrms

PreTest-PPIA404FRout_zps2c39ec9c.jpg

Voltage swing (unloaded) on the Rear channels Bridged: About 30.4 Vrms

PreTest-PPIA404RBrdg_zps074f56a2.jpg

Signals look pretty clean and close to what they should be.

Lets start the tear down.

1-refurb_zps83d329e9.jpg

Popping off the bottom cover

2-refurb_zps69913879.jpg

I bought this used off of eBay and I can tell from the Kapton (yellow) tape (not original) and rubbed off FET markings that this amp was previously reworked.

Even more reason for me to refurb it and verify that the correct parts go in it and that they are matched. FETs from different date or lot codes could have slightly different characteristics which could affect the performance of the amplifier.

3-refurb_zps70149853.jpg

You can also notice the leftover flux residue and re-soldered (shiny) pins.

4-refurb_zps1cbec9e5.jpg

Here is the power supply.

5-refurb_zps810cf51a.jpg

Look down the board

6-refurb_zpsd275ff6b.jpg

Signal input side of the board

7-refurb_zpsd8a98366.jpg

Board pulled from the chassis

8-refurb_zps9c26dd75.jpg

The bare chassis

9-refurb_zps222c3760.jpg

Top of the board

10-refurb_zps74a0ffc5.jpg

Bottom of the board

11-refurb_zpsea337529.jpg

More evidence of prior rework. Flux residue and a "FULLPACK" TO-220 MOSFET (fully plastic encapsulated). They tend to have more thermal resistance and aren't used in such amplifier designs. They would tend to be sticking up in the middle of a circuit board where thermal issues aren't as importnat and where they need to be insulated from shorting out against something.

12-refurb_zps19f054ca.jpg

Some of the old crusty thermal paste which needs to be refreshed for better thermal conductivity.

13-refurb_zps4958547d.jpg

This post sent with 100% recycled electrons.
2004 BMW M3
Mechman 280A
2 - XS Power XP3000

1 - XS Power D375

500F of Maxwell SuperCaps (soon to be 1000F)
iPadMini2

Dash mounted O-scope
Audison bitOne (Remote DRC MP)
Highs Amp - PPI Art A404
Hertz HSK130 (HSK165 waiting...)
DC Audio DC9.0K
2- DC Audio XL12m2

LEGAL             - 147.3dB @ 41Hz
OUTLAW         - 150.2dB @ 45Hz

OUTLAW         - 145.7dB @ 30Hz
JUNE 2014 SOTM WINNER

2014 COLORADO PEOPLE'S CHOICE WINNER

SOTM BUILD:
http://www.stevemeadedesigns.com/board/topic/141656-wicks-e46-m3-build-bass-turbo-button-and-a-big-new-addition/page-68#entry2802026

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Going to sound great with new mosfets. Clean for age.

http://www.stevemeadedesigns.com/board/garage/vehicle/2438-jeep-commander/


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Here are the "plugs" that PPI used to allow for easier install and removal. Notice how dirty the connection posts are. That will need some cleaning.

14-refurb_zps58b16dab.jpg

Pulling the electrolytic capacitors

15-refurb_zps32e00951.jpg

Tested the capacitors on an LCR meter to look at their condition. Still in spec and not too bad. These are the 12V input caps which smooth the B+ voltage coming into the amp. Notice PPI used 50V caps. Over rating the caps is a good idea but overrating them by 35V is excessive. I can replace them with 25V caps which will allow me to increase the amount of capacitance at the input :D

16-captest_zps40ed85c0.jpg

Here are the power rail caps. Interestingly PPI used the same value of cap for this part of the circuit. I would guess that both are compatible in each circuit and by using the same cap, PPI would be purchasing more of the same part which would lower their costs.

17-captest_zps0895eeb7.jpg

Here is my replacement for the 12V caps. I chose Panasonic 2700uF 25V caps. Still plenty of voltage rating (2x) with an increase in capacitance of 2.7x and a reduction of ESR (Equivalent Series Resistance) by 1/3. :woot:

18-captest_zpsf6717add.jpg

My selection for the power rail caps. Panasonic 1000uF 50V caps. Same value as before but you can see that the new caps do have more capacitance (987uF vs 826uF), a better Dissipation Factor and a much better ESR. A lower ESR will cause less internal heating to the cap and better release of current. Also a longer life due to less heating.

19-captest_zps07e821d9.jpg

Ready for FET removal.

20-remove_zps853e8bc2.jpg

Best way to remove the output transistors...just clip them off. ;)

21-remove_zps5336cde0.jpg

All outside FETs/transistors removed

22-removed_zpsac9061ae.jpg

This post sent with 100% recycled electrons.
2004 BMW M3
Mechman 280A
2 - XS Power XP3000

1 - XS Power D375

500F of Maxwell SuperCaps (soon to be 1000F)
iPadMini2

Dash mounted O-scope
Audison bitOne (Remote DRC MP)
Highs Amp - PPI Art A404
Hertz HSK130 (HSK165 waiting...)
DC Audio DC9.0K
2- DC Audio XL12m2

LEGAL             - 147.3dB @ 41Hz
OUTLAW         - 150.2dB @ 45Hz

OUTLAW         - 145.7dB @ 30Hz
JUNE 2014 SOTM WINNER

2014 COLORADO PEOPLE'S CHOICE WINNER

SOTM BUILD:
http://www.stevemeadedesigns.com/board/topic/141656-wicks-e46-m3-build-bass-turbo-button-and-a-big-new-addition/page-68#entry2802026

sig-sized6_zps0265e669.png

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Oxidation on the connectors

23-dirty_zps253e5f5f.jpg

Cleaned up with a "Flux Off" cleaner. Dare you to say "Flux Off" quickly ten times......... ;)

24-clean_zps628f310b.jpg

Solder on the fuse holders was a little weak looking

25-resolder_zpsf709b96b.jpg

Added some flux and re-soldered

26-flux_zps8b5eb95c.jpg

27-soldered_zps9d8bd103.jpg

28-ready_zpsbac5558d.jpg

This post sent with 100% recycled electrons.
2004 BMW M3
Mechman 280A
2 - XS Power XP3000

1 - XS Power D375

500F of Maxwell SuperCaps (soon to be 1000F)
iPadMini2

Dash mounted O-scope
Audison bitOne (Remote DRC MP)
Highs Amp - PPI Art A404
Hertz HSK130 (HSK165 waiting...)
DC Audio DC9.0K
2- DC Audio XL12m2

LEGAL             - 147.3dB @ 41Hz
OUTLAW         - 150.2dB @ 45Hz

OUTLAW         - 145.7dB @ 30Hz
JUNE 2014 SOTM WINNER

2014 COLORADO PEOPLE'S CHOICE WINNER

SOTM BUILD:
http://www.stevemeadedesigns.com/board/topic/141656-wicks-e46-m3-build-bass-turbo-button-and-a-big-new-addition/page-68#entry2802026

sig-sized6_zps0265e669.png

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Since I was upgrading parts, I looked around the board and saw the opamps

29-opamps_zpsa6893edc.jpg

LM833's are pretty basic. I did some research and found a LOT of great reviews for LM4562's.

http://www.ti.com/product/lm4562

The LM4562 is part of the ultra-low distortion, low-noise, high-slew-rate operational amplifier series optimized and fully specified for high-performance, high-fidelity applications. The LM4562 audio operational amplifiers deliver superior audio signal amplification for outstanding audio performance. The LM4562 combines extremely low voltage noise density (2.7nV/√Hz) with vanishingly low THD+N (0.00003%) to easily satisfy the most demanding audio applications. To ensure that the most challenging loads are driven without compromise, the LM4562 has a high slew rate of ±20V/µs and an output current capability of ±26mA. Further, dynamic range is maximized by an output stage that drives 2kΩ loads to within 1V of either power supply voltage and to within 1.4V when driving 600Ω loads.

They're also relatively cheap.

DigiKey had them for ~$3ea

30-opampsremoved_zpsfefb5bac.jpg

Installed the new opamps

31-newopamps_zps939fd48d.jpg

32-opampclose_zps593b33b8.jpg

Time for the new FETs and transistors :D

The power supply used IRFZ44's which are rated at 60V and 57A with 230A of pulsed current and 12mOhms of On-resistance.

I selected ST STP75NF75 FETs to replace them which are rated at 75V and 80A with 320A of pulsed current and 11mOhms of On-resistance.

These are the same parts I used in my Rockford Fosgate Punch200DSM refurb and its worked great over the past year.

33-psufets_zpsac5f2fbf.jpg

Power supply rectifiers were a combination of ST BYW29F and Vishay FESF8DT. Rated at 8A.

I didn't like using a combination of two different parts so I replaced them all with ON Semi MUR1520 which are rated at 15A.

34-rectifiers_zps3d760a9e.jpg

12V Input caps ready to be installed.

35-12vcaps_zps7e355fc5.jpg

Inserted

36-12vcapsin_zps4146615f.jpg

Here's a trick if you need to flip the board over to solder the parts and don't want them to fall out, just flare the leads out.

37-caplegs_zps236d9c51.jpg

Rail caps ready

38-railcaps_zps80f9ac9f.jpg

PPI uses transistors in the output section rather then MOSFETs so I had to make sure to replace them with appropriate parts.

The board had BDT81 and complimentary BDT82 transistors which are rated for 60V and 15A.

I couldn't even find those parts anymore so I needed to look for a similar replacement.

I found ON Semi 2N6488 and 2N6491 transistors rated at 80V and 15A. These are widely used and well regarded

You need complimentary NPN and PNP parts as one conducts the positive voltage rail and the other conducts the negative power rail.

Parts loaded :good:

39-done1_zpsfb4a0daf.jpg

40-done2_zpsb10ea9eb.jpg

41-donebottom_zpsff834e4b.jpg

This post sent with 100% recycled electrons.
2004 BMW M3
Mechman 280A
2 - XS Power XP3000

1 - XS Power D375

500F of Maxwell SuperCaps (soon to be 1000F)
iPadMini2

Dash mounted O-scope
Audison bitOne (Remote DRC MP)
Highs Amp - PPI Art A404
Hertz HSK130 (HSK165 waiting...)
DC Audio DC9.0K
2- DC Audio XL12m2

LEGAL             - 147.3dB @ 41Hz
OUTLAW         - 150.2dB @ 45Hz

OUTLAW         - 145.7dB @ 30Hz
JUNE 2014 SOTM WINNER

2014 COLORADO PEOPLE'S CHOICE WINNER

SOTM BUILD:
http://www.stevemeadedesigns.com/board/topic/141656-wicks-e46-m3-build-bass-turbo-button-and-a-big-new-addition/page-68#entry2802026

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Looking at the bare chassis, it has a bunch of old crusty thermal paste on it

42-oldpaste_zpsfea214c5.jpg

Thermal paste is MESSY so I decided to just rip off the old tape and add some new.

43-removekapton_zps41540625.jpg

New tape ready to go

44-newkapton_zps5e37cbc4.jpg

The Kapton tape (or mica sheets) are needed to insulate the FETs/transistors as the metal tab is exposed to the rail voltage which would short out on the chassis otherwise.

Ready for new thermal paste

45-prepboard_zps2d423b17.jpg

Test fit before I add the messy new paste. All parts fit evenly against the chassis. :good:

46-fettestfit_zps06eb2055.jpg

Paste added and board installed

47-newpaste_zps84e69e01.jpg

48-boardinstall_zps309fff69.jpg

This is the bottom cover, notice all the "fingers". PPI uses those fingers to hold down all the FETs/transistors. Therefore you should NEVER run an old PPI amp without the bottom cover. Some of the parts could easily overheat. I'm not a big fan of this design, but it is what it is.

49-bottom_zps304f2ffa.jpg

As a precaution, I used a needle nose pliers and bent all the fingers out a little to make sure they all made good contact.

50-bottomtabs_zps1f4feb30.jpg

Bottom installed

51-bottominstall_zps4912aca4.jpg

BOOM

Refurb complete!

52-done_zps89ddf512.jpg

Time for testing! :D

This post sent with 100% recycled electrons.
2004 BMW M3
Mechman 280A
2 - XS Power XP3000

1 - XS Power D375

500F of Maxwell SuperCaps (soon to be 1000F)
iPadMini2

Dash mounted O-scope
Audison bitOne (Remote DRC MP)
Highs Amp - PPI Art A404
Hertz HSK130 (HSK165 waiting...)
DC Audio DC9.0K
2- DC Audio XL12m2

LEGAL             - 147.3dB @ 41Hz
OUTLAW         - 150.2dB @ 45Hz

OUTLAW         - 145.7dB @ 30Hz
JUNE 2014 SOTM WINNER

2014 COLORADO PEOPLE'S CHOICE WINNER

SOTM BUILD:
http://www.stevemeadedesigns.com/board/topic/141656-wicks-e46-m3-build-bass-turbo-button-and-a-big-new-addition/page-68#entry2802026

sig-sized6_zps0265e669.png

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I connected the amp to a bench power supply and fed it a test tone with my iPhone.

Here's the unloaded voltage swing on the Front Right channel, same one I checked before the test. 15.9 Vrms.

a404FRV_zpse3d763cd.jpg

Here is the rear bridged channels. 31.4 Vrms

a404RBRDGV_zpsafe791af.jpg

Minor improvements but I didn't expect it to be anything drastic.

The unit works and the signals are CLEAN.

I'd love to send this to BIGDWiz and see just how clean it is, especially with the new opamps... ;)

I connected a 4ohm power resistor load to the amp to pull some current through it.

Here is a front channel

a404FrontP_zpsed2e1ae3.jpg

Here is a rear channel

a404RearP_zpsbe368deb.jpg

Looks like a solid, consistent and unclipped 56W per channel which is right on the specs. :D

Can't wait to get this in the M3 and really give it a test run. :drinks:

This post sent with 100% recycled electrons.
2004 BMW M3
Mechman 280A
2 - XS Power XP3000

1 - XS Power D375

500F of Maxwell SuperCaps (soon to be 1000F)
iPadMini2

Dash mounted O-scope
Audison bitOne (Remote DRC MP)
Highs Amp - PPI Art A404
Hertz HSK130 (HSK165 waiting...)
DC Audio DC9.0K
2- DC Audio XL12m2

LEGAL             - 147.3dB @ 41Hz
OUTLAW         - 150.2dB @ 45Hz

OUTLAW         - 145.7dB @ 30Hz
JUNE 2014 SOTM WINNER

2014 COLORADO PEOPLE'S CHOICE WINNER

SOTM BUILD:
http://www.stevemeadedesigns.com/board/topic/141656-wicks-e46-m3-build-bass-turbo-button-and-a-big-new-addition/page-68#entry2802026

sig-sized6_zps0265e669.png

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