Low Recording Levels Portastudio 424 MK II ?

[CraigMcLane]

Hey everyone,

i am currently trying to get an 242 MK II running correctly, or at least in a condition that i can use it for recording.
My main problem at the moment is that the recordings are very quiet (at least compared to my expectations).

Since it is my first Cassette Multitrack my first question is: Is it a general thing that i have to push the input Level to +6 dB into the red (with DBX OFF) to get a playback level of around 0 db or is it more likely that something is broken?
With DBX ON i get around -6 dB playback Level.

The db-levels readings are taken from the single-channel Meters (1,2,3,4) not L/R.
When i record with 0 dB input levels the Playback levels are between -10 dB and -6 dB with DBX off. With DBX on only the first (lowest) level-led lits up slightly.

Channel 1 and four seem to be behave identical, channel 2 is a more quiet and channel 3 a little bit louder compared to 1 and 4. Besides this the above behaviour is the same on all 4 Channels.

Second Question:
Do you have any tips on where to start to get Channel 2 on the same Level as the others?

The playback function itself seems to work correctly since normal tapes (bought or recorded an another tape Deck) level around 0 db.

What i have done so far:
- cleaning the mechanical parts and heads of the cassette player
- demagnetizing tape heads
- opened and cleaned all pots and switches which solved all noise and crackling issues

Thank you for any tips and experiences with these machines and also for this forum
toby

 

[SkywaveTDR]

A unit from 1996 which is on the service manual might need work on it by now- decayed power supply and also all kinds of time for people to abuse these. You do not state what tape you record on. I test them with Maxell XL II tape. I have known some Chrome tape that comes from Korea has 5dB low print level- that is why Korea had it as BASF could not sell it one people found out how it works. If the play is OK, then I would go through the service manual with regard to input levels check. I had had units come in with input chips blown out as the input were subjected to amplifier outputs which can be like +/- 45V while this unit is not designed to take that. The true answer can only be found at a Technical service facility and there are not too many of those any more- that is the ones that know what they are doing. Porta Studios that have been known to have switch dirt in them. It has to be tested with proper input levels at 1KHz and as the manual directs. If the input section passes all test then it can be circuits in the record section and even interconnection that get intermittent or have broken solder joints- wave solder production is not a mil grade soldering as it is very weak and it only take a amount of dropping or rough handling to break them. I have seen this on all Porta Studios.

 

[CraigMcLane]

Hey,
thank you for answering and pointing out some places to start.
I tested with BASF Chrome Super II and BASF chromdioxid SM cassette. It has been the same behaviour with both Tapes. I just made another test at 1 KHz (Sine Wave) but the result is still the same.

I think i will start working my way through the service manual to test and adjust and hopefully it lets me find some clues where too look next.

 

[SkywaveTDR]

Teac and Tascam unit have a long history of trouble with BASF Chrome tapes- I had found that the tape has low output or print levels. This was even more so in the NAC 399 tape which required the modification of record amps- once that was done none of the Japanese tapes would work with that mod. Having talked with Don Morris of RMGI he told me that some of that Chrome tape was dumped to Korea because it had bad sales results. They are still now selling it and NAC was selling it under the high grade 399 model while the 771 which was good tape ran out. I would tell you to get a Maxell XL II or a TDK SA and do that test again. When power supplies start to decay and lower voltage due to bad caps. The amplification gain will suffer and even bias levels will get less. It might be a tape issue or a deck power supply issue but also maybe bad caps in the record section. I would have a look and where 10V caps are seen to replace those with 16Vdc well known caps NOT Marcon. Record gain might be enhanced that way. Clean the heads- many people use Isopropyl alcohol which is for the skin previous to injections. This is NOT the right alcohol but Denatured from the hardware store is- I have used denatured (Ethanol) for like 50 years. I have seen heads with Iso cleaning still covered in oxides- it works as well as water.