Series 5000 MOSFET stereo power amplifier - Upgrades

[Leinster Lad]

15 hours ago, AntonEB said:

I have read all the preceding comments with great interest, as I recently scratched out my "beginnings" of the ETI 5000 Amplifier kit build. ay back in the 1980's I bought a Hitachi MOSFET Amp (HA-7700) that utilises the slightly lower spec MOSFETs from Hitachi (2SJ48's and 2SK133's). I still have it today and it has amazing sound.

 

Because I owned this amplifier, I was most intrigued by the article in the ETI publication way back. I started with great intensions to build this amp, purely for the experience but never got down to actually building it.

 

Over the years I have relocated residence a few times and my boxes of goodies just followed me around. I recently retired form employment and started sorting out my stuff and I was so excited to find my set of (Hitachi J50's and K135's), my two circuit boards and the mains transformer I bought for the project.

 

To my great frustration I cannot find my documentation to build the amplifier.

 

I would really appreciate your assistance if one of you could share, with me, the schematic diagram, component list and the circuit board layout.

 

It will a whole lot more exciting to tackle now that I have read all of the development improvements in the above chat.

 

In great anticipation.... thanks for sharing all of your experience and skill above.

 

 

 

What you seek can be found .......  Here    ( please note that I am not the owner of these documents )

 

The ETI477 / Series 5000 amp was published in ETI 1981 Jan, Feb, March

[Monkeyboi]

I forgot about those archives.  Pity there are so few of the Electronics Australia editions.

 

Cheers,

Alan R.

[Leinster Lad]

Got an answer from the diyAudio forum regarding the zener and NFB mods.

The zener is self explanatory.

You can clearly see that the track between the collectors of Q5 & Q7 is cut.

 

The NFB ( R19 22K) now gets connected to the exact same point as L1 (inductor)

In the picture, you can just see the tail of R19 running parallel to the track and terminating at L1

 

I am guessing that this gives a more accurate reference point of the output signal ( without any variations caused by current flow )

Like the theory behind a star point ground system.

 

[WINEDS]

The green cap in the lower left corner is effectively soldered to the same track at both ends? 

[Leinster Lad]

No, it is insulated from the track via a TO3 bush.

The bolt goes thru the board and connects to the heat-sink.

The cap ties the  0 volt rail to ground at RF , but isolates at DC.

[Leinster Lad]

Getting geared up to restore my old ETI Series 5000 power amp (which uses the ETI 477 David Tilbrook designed mosfet boards )

I was not happy with the original boards, as some of the tracks lifted when I depopulated them.

 

So, after a LOT of pain etc, I managed to copy the board design, created the Gerber file and had some (10) new boards made !

 

So if anyone needs a new board or two, hit me up !

[MarcAL]

Hi Leinster Lad,

 

It's good to hear from you again and getting back onto this project.

 

I noticed that the boards are not drilled so I figured that one could use one of the old boards as a template and drill through that to keep it as accurate as the original.

 

The soldering of the tracks would be a thing to sort out and would be open to suggestions.

 

I'll PM you about these magnificent boards shortly.

 

Keep up the good work!!

 

MarcAL.

Edited June 22, 2020 by MarcAL

[Leinster Lad]

Hi MarcAl, nice to hear from you as well !

 

You are correct about the boards being undrilled.

I will use one of my old (naked) boards as a drill template, so I wasn't worried about creating a "drill file" for the PCB manufacturer (I also had no idea how to create one, so the decision was easy)

 

I also have a couple of mods that I want to do which might require different size holes, so I have left my options open. (i.e. screw connectors for power inputs and output etc.) 

The 18v zener

10 turn pot for the mosfets bias, or even a daughter board for the bias  as per the EAM6000 amp.

Maybe clipping indicators as per the EAN6000 as well.

Actually lots of ideas from your previous rebuild as well as the good folk over at diyAudio.

 

I may also split the power supply between the drive side (regulated) and the output side (unregulated) at the fuses ? (like Naim do ?)

Not really sure yet. I have got myself a scope and you-tube , so I will be experimenting a bit !

 

Hope I don't let too  much smoke out !!

 

Regards

Dave

[Leinster Lad]

On 24/11/2018 at 2:01 PM, Leinster Lad said:

 

What you seek can be found .......  Here    ( please note that I am not the owner of these documents )

 

The ETI477 / Series 5000 amp was published in ETI 1981 Jan, Feb, March

Archives are now gone.

I think SC sent him a lawyers letter for copyright breach ?

 

Anyway, I have scanned a heap of my SC and ETI mags if anyone needs a specific article.

[mwhouston]

Just stumbled on this. Very nice build from a classic amp module. Built two of the 50W myself and one 175W. 175W is my subby amp with my TV system. 

[mwhouston]

Oops, I’m we’re the bipolar amps. I did build just one of these as a guitar amp. 

[Gordon Macfarlane]

Have been tempted over the years to buy a pair of these. Haven't got  round to it yet but they do look the part to my layman's eyes :

https://connexelectronic.com/product/aem6000-audio-amplifier-with-heatsink/

Edited August 12, 2020 by Ozcall

[Leinster Lad]

Me too. These are an updated and improved version of the old AEM6000 amp.

Apparently there is quite a controversy  surrounding these over on the diyAudio forum !

AEM6000_Audio_Amplifier_Module.pdf

[WINEDS]

On 12/08/2020 at 5:34 PM, Ozcall said:

Have been tempted over the years to buy a pair of these. Haven't got  round to it yet but they do look the part to my layman's eyes :

https://connexelectronic.com/product/aem6000-audio-amplifier-with-heatsink/

 

They are a rip off of diy audio member suzyj rework of the original design.

 

https://www.diyaudio.com/forums/solid-state/288479-aem-6000-ready-build-post5555673.html

Edited August 15, 2020 by WINEDS

[Leinster Lad]

Yep, they certainly did rip Suzy off.

From what I have read, she designed and developed an absolutely cracking amp.

Unfortunately, she is not (able?) to support her work and sell boards etc.

 

These connex guys have just filled a vacuum created by that. Sad really. I'd by a pair of her boards in a heart beat.

[WINEDS]

21 minutes ago, Leinster Lad said:

Yep, they certainly did rip Suzy off.

From what I have read, she designed and developed an absolutely cracking amp.

Unfortunately, she is not (able?) to support her work and sell boards etc.

 

These connex guys have just filled a vacuum created by that. Sad really. I'd by a pair of her boards in a heart beat.

I don't think she needs to sell boards to support her work.  She appears to be a csiro engineer and scientist.

Edited August 15, 2020 by WINEDS

[Leinster Lad]

I didn't mean support as in financially. Just meant in the sense of her sharing her work with the diy audio community

 

[Gordon Macfarlane]

Well won't be buying those then.

[Leinster Lad]

Just a quick update on my series 5000 rebuild.

 

I've got the new case , soft starts and power supply boards.

 

Just starting to play with the lay out.

 

Heaps of room now with this deeper case. Original front heatsink bolts onto the front with minimal mods.

 

I've got two partitions which the trannies, soft-starts and pwr supplies bolt onto. Any EMF should be contained and being modular, really easy to remove to trouble shoot.

 

some pics...

 

[Leinster Lad]

The chassis is starting to take shape.

Decided to add 10mm ally bar to the bottom to allow the original front heatsink to fit correctly.

The two 16mm holes on the rear panel are for 15-0-15 vac output.

I will use one of them to power my series 5000 pre-amp. (next project)

The other will be for generic purpose. Anything that requires a dual 15vac supply.

I plan to use it to feed a 5v LPS that will power my squeezebox touch.

These 15vac supplies are sourced from aux windings on the original Ferguson transformers.

[MarcAL]

This is amazing Leinster Lad, the chassis is coming along quite nicely.

Very nice power supplies and soft starters with plenty of room for any future additions.

 

One of the latest upgrades that I made recently was replacing the input coupling capacitor with a Nichicon Muse ES 2.2uF bipolar.

I also have replaced all of the previous silvered mica types from a previous side-grade modification with polystyrene types and wow this really made a significant difference!

The amplifier now sounds a whole lot nicer than before with clarity beyond belief.

More tweaks to be done as I am still open for ideas.

 

Keep up the good work and hope to be looking for progress reports to come.

Edited September 14, 2020 by MarcAL

[Leinster Lad]

Thanks Marcus, I'm pretty happy so far.

Just a couple more bits and pieces to do on the chassis. Waiting for M4 spacers and screws to mount the trannies and some rubber grommets to protect wiring etc.

Then on to drilling and populating the boards.

Could you list the mica caps replaced with polystyrene types ( are they MKP ? Wima or ??? )

 

Actually can't wait to get it going !

 

Aiming to have everything secured to either the front, side or rear panels, leaving the top and bottom easily removable for access.

 

The internal panels that thye trannies, soft starts and pwr supplies bolt to should act as a faraday cage for the mains wiring and trannies etc.  DC stuff is on the outside of that cage. The only Ac that will be on the DC side is the trannie secondaries connecting to the pwr supply boards. Maybe 1 inch of wiring at most.

 

Speaker wiring will run along the bottom, straight from the boards to the binding posts, passing under the trannie "module"

 

Input coax will run around the non AC side. giving distance away from speaker cables, trannies and DC wiring.

 

With the soft starts, i think i'll be able to run 1 amp fast blow fuses, possibly being able to do away with the rail fuses on the boards. ?

 

Will need to experiment with this.

 

 

 

 

 

 

Will be clear when I get some more pics up.

Edited September 14, 2020 by Leinster Lad

[Leinster Lad]

Aux 15-0-15 output sockets on rear panel and rubber feet.

The added section can be seen in these pics.

[MarcAL]

Hi Leinster Lad,

 

I have replaced most of the capacitors on the 477 modules with:

C2, C3, C4, C6 and C15 with polystyrene types that can be purchased from Element14.

C7 and C8 stayed the same, ceramic.

C1 with a Nichicon Muse ES Bipolar type.

C5 with an ELNA Silmic II Electrolytic.

C12 and C13 with ELNA Cerafine electrolytics.

C9, C10, C11 with metalised polypropylene.

I am happy with the choices so far as it does sound very clean and detailed now to the point of extreme happiness.

With my next step I may replace all of the resistors with Vishay types including the 0R22 non inductive wire wounds.

When I do this I may populate the new boards and then perform an A-B test on the amp to verify any further component changes and the improvements associated with such a task.

Any suggestions with this would be greatly appreciated.

 

MarcAL.

Edited September 17, 2020 by MarcAL

[Leinster Lad]

Great info Marcus, thanks !

 

I was wondering what you have done with  C14 (220p) ?  I think that is the "Miller" cap and is one of the most critical components for stability and to stop oscillation.

I think this was the bugger that initially failed on one of my boards that consequently allowed the magic smoke to escape.

This cap is listed as a ceramic.

Some chatter over on the DiyAudio forum indicates that a silver mica is the go for this cap.

 

Have you looked into this ?