Ampeg's whole porta-flex line has recurring problems except for the tube porta-flex amps. Read the reviews. This has gone on for years now. Ampeg knows the failure rate is stupid high but the new ones still have the same problems. And don't even try to run them at 4ohm for any length of time at high volume or when it's hot out. They almost always go into fault/thermal shutdown. Ampeg used to be known for reliability. Now they are anything but except for their tube amps and even they're not built like they used to be. It's a shame.
This is part of the reason we live in a throw away society. The bench hours required to troubleshoot, the replacement components and the re-assembly and testing of the unit most likely comes close or if not exceeds the cost of a brand new head. $349 US
I have one on my bench that works but at a very low volume. i have to crank it up to maximum to get half the volume of an Ampeg b115 (150w). I found that i have +80v/-80v where it should be +55v/-55v according to the schematic. the weird thing is that i could not find a single broken component.
I am trying to repair one. Unit now powers up, fault light off, BUT irs209057 chip will not start up. CSD pin held low at 3.3v ( should be nearer 10v). Replaced chip and most of the surrounding devices. No joy. Rails are +/- 75v vs 55v as expected. This may be due to power amp not being on, due to the fault? Other than that other voltages on irs209057 appear reasonable. Any tips? I’m stuck!!!
I am writing to inquire about an issue of my Markbass CMD151P Jeff Berlin amplifier. I turned the amp on and practised for about 5-10 minutes. The sound was good, bright, full, nice. After that, the sound started to be weak, volume is little bit down, feeling is hard to play and not responsive. So, I stopped to play and wait for about 5 minutes (wait with turn the amp off or wait without turn the amp off), the sound became full and rich again but only for 2-3 minutes. Then again the same issueis appeared. Even though the offical service in my country (Turkey) couldn't reilize an issue, they accepted to replace my amplifier with a new one. The issuse pursued in the new amp and I decided to change other elemets; my guitar has also replaced other related parts such as socket etc. However, the issue is still exist. I started to belive the issue can be from a specific batch production. I would appeciate if you help me to solve this problem or give technical advice and check procedure that I can apply as an Electronic Technicihan.
