ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Good day everyone.
I bought Beomaster 1500 receiver and have the following issue:
The sound from tape and phono inputs is fine. Sound from FM section has almost no low end. The quality of stations reception itself is ok, stereo indicator is working. Output level is comparable to tape/phono inputs, just no bass. No difference between L/R channel.
What has been done:
- Replaced following caps in stereo decoder part : C55, C52, C51,C61,C69,C68,C76,C77
Need to mention that after changing C61,C69 I got good sound (with good bass) after turning on, but fading away after 2-3 seconds. Unfortunately after several on/off cycles I was not able to reconstruct the situation any more.
- As mentioned in MC1310 datasheet I tried to play around with different capacity and resistance of de-emphasis section (R74-C67 / C75-R81). There are changes in treble character but no influence on low end.
- I even ordered new MC1310p and replaced it. Tried to change the input voltage (R59 resistor) in range of 9-13 volts – no effect
- One of the ideas was pure contact in phono/fm switch through which the connection of signal to amplification part is made. Bypassed it - no results.
Any ideas what can be the reason?
scheme part 2
Up
I have localised the problem: bypassing the group of elements between c61 and tr8 (c69 and tr9) gives me juicy low end sound. Bypassed part is 5 order low pass elliptical filter. All caps are in nominal. Tried to tune the both inductions L12/L13, no effect. Any suggestions, community
Change of inductors resolved the issue