Herlev, 15. Jan. 2004
Repair procedure for older versions IA150B and PA150B rev.8
The main problem in over 90% of the repair cases concerning these unit types has been that the
electrolytic capacitors originally used dried out relatively quickly and caused internal oscillation
similar to the IA/PA250BmkI problems as well as overheating voltage regulators, which in turn
created multiple faults ranging from humming and switching noise to total AC burnout of resistors
and capacitors.
The solution is therefore based on preventing the drying out and the following oscillation from
occurring in the first place. This is ensured by using ceramic capacitors instead of electrolytic
capacitors that cannot dry out, since these do not contain liquid.
The original specification featuring normal type capacitors capable of work temperatures up to
90deg C should have been fully adequate, since the main board temperature never rises above
approximately 60deg C. The theoretical lifespan was therefore originally conservatively estimated to
be not less than ten years.
The following electrolytic capacitors marked red need to be exchanged to the mentioned ceramic
capacitors or tantal capacitors
C17 – 117 – 344 – changed from 3u3 50V to
C18 – 118 – 345 - 349 – 352 changed from 3u3 50V to
C346 – 347 changed from 3u3 50V to
C348 – 350 changed from 3u3 50V to
This should according to R&D be the ultimate solution. It has been tested thoroughly in laboratory
conditions, where the test units have been provoked in several abusive ways including high work
temperature and higher voltage without boiling or oscillating. IA and PA150B now appear to be
completely up to standard in terms of longevity compared with the rest of Thule’s amplifier
programme. We sincerely hope R&D’s efforts will be of use to you all.
Please note that these revisions are only useable on ver.8 (today’s standard, changed in 1999).
Earlier versions should have their main boards changed if oscillation has occurred. These component
changes have now been implemented in production.
marked green
100n 50V
470n 16V
:
220n 50V
2u2 35V Tantal
Thule Audio ApS Telephone: Internet: Bank: Den Danske Bank A/S Giro account no.: 6 96 72 13
Hørkær 14 +45 44 94 6000 www.thule-audio.com Account no.: 3140 255793
2730 Herlev Telefax: E-mail:
Denmark +45 4494 6880 thule-audio@email.dk S.W.I.F.T. address: DABADKKK CVR/VAT no.: DK 13 48 45 97
Loading...