Thule Audio SPIRIT PA150B, EM 1015 (German model marking "Taboo") Bridged 2x 150W Power Amplifier - Variants and Mods

[tiefbassuebertr]

For replace the speaker protection relays and main switch on rear panel I have in the moment two different PA150B on the desk. I would like to use this opportunity to provide a description of early modifications I made to this model between 2003 and 2010.

Outside images of this model with serial-No 2143031 (used main board EM1015 Rev7 or newer) are to find in image No 2-5 and No 7-9

In the attached schematic you will find also the preamp section - this means, it is the integrated amp version IA150B (EM1015, Rev0).
Unfortunately this schematic is not in all details identical to these devices of this model - but it is better than nothing.

I know two different PCB-versions, both with dual mono power supply (and both used for the integrated amp IA150B and power amp version PA150B) :

1) Mainboard EM1015 <rev.7 (offered 1997- 1999) for each channel with one BHC (Aerovox) T-Power elcap C25/C26 - go to image No 10 and No 11 and
https://www.dnm.co.uk/capbhc.html
and one usual elcap 10.000uF/63V C27/C28 (image No 12) in the kind of this under
https://www.rs-online.vn/p/capacitor-snap-in-series-158-10000uf-63v/8773715/
so as voltage regulators LM317/337 in a SO-8 outline behind the voltage doubler circuit for the front end (differential amp + VAS) of power amplifier.
Basic description under
https://www.electronics-tutorials.ws/blog/voltage-multiplier-circuit.html

2) Mainboard EM1015 rev7 (offered after 1999) without BHC T-Power for C25/C26 instead this also only two usual (same) elcaps like C27/C28 (image No 12) in the kind of this:
https://www.rs-online.vn/p/capacitor-snap-in-series-158-10000uf-63v/8773715/
so as voltage regulators LM317/337, now in a TO220 instead the SO-8 outline used in the previous PCB versions

In both versions it is important to perform modification steps as follow in order to increasing reliability and reducing thermal stress as to see in image No: 6 around the mentioned voltage regulators - in the attached schematic (first image) Reg 7 - Reg 10

1) Removing the voltage doubler circuit for the front end completely (because no space present for voltage regulator heat sinks in necessary sizes).
more details and consequences are to read in post #13 under
https://www.diyaudio.com/community/threads/repair-thule-ia150b-no-sound-except-humming.303712/
BTW - this integrated amp from this topic use also the above mentioned main board versions.

2) Introducing an additional zobel network before relay switch contact (image 13-15, R15/C57 so as R115/C157 in the attached schematic diagram) are in real live not in use and the already present zobel network R220/221 and C204/205 on main PCB are behind the relay contact and only in operation when the speaker relay is switched on.

The additional modification step, which I had perform on main board EM1015 <rev.7, is as follow:
The BHC (Aerovox) T-Power elcap C25 and C26 was replace by the same usual elcap version as for C27 and C28. For getting similar sonic results as with BHC T-Power I introduce resistors 0R22 between C25 and C27 so as C26 and C28 (both in the "+" and the "-" rail) - check out images in post #2.
The main disadvantage of BHC T-Power caps was the very short life time. The excellent sonic performance with this caps was only present in the first few months of use and for this reason Thule Audio has decided to use usual Elcap versions from Rev. 7 onwards.

 

[tiefbassuebertr]

In the attachment here are to find the mods on the PA150B device with main board EM1015 Rev6-7, Se‪r.-No 2042013, which I have made several years ago.
The currently work only concerns the replacement of the speaker protect relays by the type from the attached datasheet from SDS S4.
Because the coil connections have a predetermined polarity, the connection sequence had to be swapped for one relay - go to image No 12 and No 13.

The used main switch in poor quality wasn't replace. It was shorted by a wire due an exist outdoor switch with integrated inrush current limiter.

 

[ostripper]

Ouch . the poor .... poor - poooor old Thule !! That's German engineering - blasphemy...
OS

 

[tiefbassuebertr]

PA150B EM1015 rv.7 Ser.-No 9826177: Same mod steps than in post #2
The mentioned main board EM1015 from Se‪r.-No 2042013 in post #2 is below rv.7. (maybe rv.6 or rv.5)
Unfortunately the rv. No isn't to find on PCB (like rv.7 on image No 1+2 in this post)

 

[tiefbassuebertr]

PA150B EM1015 rv.7 Ser.-No 9826177: Same mod steps than in post #2 - more images