Tamp TA1400 clipping problem

Because the circuit is a fairly simply class B design, low power clipping is normally down to a output or driver transistor fault, i assume you have checked internal fuse etc ??, are they intact ???. Because there is an op-amp pre-driver chip check that this also has the correct voltages on pins 4 & 8 (normally 12 or 15 volts).


Edited by simonp1100 - 08 October 2017 at 5:52pm

Yes, your correct it's a class H, have you checked the output devices, this normally is the first thing i would check along with fuses. As regards not switching over to the higher rail this can be seen if you have a scope.

Edited by simonp1100 - 08 October 2017 at 5:59pm

kedwardsleisure wrote: and for goodness sake dont try using it in bridge if it isn't capable of working correctly in Stereo.

on the diagram I have here the first 3 leds are input level, the clip led is driven from the error amplifier and the fault led is off the protect circuit.

So an input level fault wouldnt necessarily bring the clip led on but an output or psu stage would.

The pots on the back of the front pcb should be adjusted so the signal drives the limiters at the right point. When adjusted properly the clip light should barely blip on the signal peaks and gradually reduce in intensity as the limiter integrator brings the gain down (it grounds the wiper of the front volume pot!).

I would do the following:--

1. Take out class H switching FET's on channel B (positive & negative), see if channel B is distorted with input signal. Just because you have measured the waveform at the gate of the FET, this tells me that the signal is present BUT still could be a faulty FET. Have you checked FET isolation on heatsink & taken out FET's and measured them ?????.
2. Check on both channels the positive & negative switching waveforms on the gates of all four high / low switching FETS (should be the same point / voltage on both channels).
3. Check class H switching diodes (take out of circuit and measure, as well as short on heatsink).


If channel B is working fine (i.e. no distortion) on the lower positive & negative voltage rail (115V), then it would indicate a Class H problem & i would still go with FET's & switching diodes.

Let use know how you get on.

kedwardsleisure wrote: can we see a snapshot of the scope ?

Edited by Tonskulus - 30 October 2017 at 12:59pm